'm merely dealing with the fact that there is a choice made to lie/not divulge the truth. On this basic tenet, they both dropped the ball: Oliver back in S4, Felicity right now.
I'd list season three for Oliver as well but yeah, sure, Felicity I'm sure will ultimately be proved to have made a mistake and chances are a rather big one. I have no problem acknowledging that nor do I have a problem with that. I've never been the one that claims she's viewed or treated as perfect. ( I actually don't think that most of her fans claim that either but that's a different topic)
The Helix dilemma is, in its most general terms, the idea that teammates shouldn't keep secrets from each other, if being a team means they have to be able to count on each other and trust one another. No one is saying that anyone on that team is a pillar of trustworthiness, obviously not secret-keeping champion Oliver.

Oliver's serial secret-keeping does not invalidate or dilute the principle that teammates shouldn't keep secrets, conceal the truth, obscure facts that could impact how the team works, or -at the extreme- if they can prevail or survive against an enemy.

TPTB are playing the trust card here and I do feel that they are trying to give Felicity a glimpse (as decaf mild roast as it may be) of Oliver's ethical quandries along his journey. They may even be trying to sell the idea that the Helix arc will be her version of Oliver's five years in hell -- not sure if viewers will buy it or make the parallel. It remains to be seen.

Oliver being a poor example of divulging truth to his teammates does not cancel out Felicity's (or any Team Arrow member's) obligation as a team member to not keep secrets that could impact the team's activities. Whether she's a documented Queen employee, contractor, freelancer, getting a pension or not, or a volunteer is beside the point -- if you're doing work on behalf of Team Arrow, you're on Team Arrow. Quentin's not working in the cave, but he's as much a part of Team Arrow as anyone else ... even if he's drawing a municipal salary.
See I don't actually disagree with most of this (I differ on how much she's currently messing up and how though) It's just that some are already trying to frame what she's doing with Helix as the same as what Oliver was doing with the kid and that's what I reject 100%. Let the show explore why in other circumstances one might feel like they need to keep secrets but the kid thing the way it played out should not be the comparison.

This choice should come with real consequences that won't be just brushed away. If any other team member pulled this, I suspect a segment of the fandom would be all over them on how they betrayed the trust of the team, how they failed Oliver, how could they ever be counted on again, etc. They'd drum up a Star Chamber and take the person to task, with no right of appeal. Not saying Felicity deserves such treatment, only that she shouldn't get a total pass on it.
I guess for me, this is a big place we differ in opinion. I just wouldn't react that way even with another team member.

I mean I was willing to let Evelyn off the hook for trying to kill the team last season when she was blaming them for not rescuing her from DD (when they didn't know she was even a prisoner). And I'd be fine with putting her on a bus to restart her life as a normal kid if she had another change of heart about Prometheus. (But out and out betrayal does take actual trust off the table with her)

An even better case in point is when Quentin was actually working with DD. Sure, I called him foolish and waited for it to explode in his face but I never felt he couldn't be trusted after that or that his actions were intended as a betrayal, even when he straight up KNEW DD was a murderer.

At this point, all Felicity can be judged on is pretty naively assuming the best of the group without any proof that they aren't doing bad things, but proving a negative is usually pretty hard. So like I did with Quentin, I'm shaking my head, calling her foolish and waiting for all of this to implode on her, but I'm not actually giving her any special treatment or treating her any kinder than I would another team member when I do so.

And really, at this point special treatment wouldn't even be required. She hasn't actually even done anything too bad yet.

She's not working against the team (though I expect at some point they will be at odds with her thinking her way is better but even that would be up for interpretation as to who is right depending on how it plays out) She's using Helix as a resource FOR the team.

She is keeping Helix and before that Pandora not exactly secret but hasn't been letting people in on it all the way and really, it's not that she has this information that was the problem, but how her grief and trauma (I'm lumping all of it not just Billy) has led her to be ok with doing more morally questionable things. I guess the issue of lying or keeping secrets seems like a lesser issue to me.

And again, I have a bit of difficulty in understanding why she is actually keeping the truth about Pandora or Helix a secret since no one has cared in the past how she's done what she does for the team so it's kind of a grey area for me if anything would have changed even if she had been totally upfront and told everyone she was getting some help from this other group. All she's ever done is hack into this or that computer or file or agency and use this or that program to enable what she does. Anytime she tries to explain the steps, they make her stop and skip ahead to the end result. In the episode Oliver even says he doesn't care how she got her results when he knew they came from what she was keeping secret from him. So yeah, it's hard to get too upset about her actions at this point.

If the issues is keeping secrets from your teammates is always bad, then sure, she's messing up but I don't think the show has said that full disclosure about everything in everyone's life has to happen. Stuff that affects the team should be shared, but at this point I think Felicity is thinking that Helix and her involvement does not affect the team. I'm not yet sure that they do actually affect the team.

I mean technically even when the team were trying to get a hold of her and she didn't get back to them, she'd already done what they really needed from her. She wasn't hampering them in the team mission. She was causing them to worry but one of the saddest points in the episode was the SURPRISE on Felicity's face when Oliver explained he was worried about her actions. That's the point their relationship has been reduced to this season. She's surprised when Oliver is personally concerned about her.

Again, when he pointed out that secret keeping generally doesn't end well, she agreed that he was right but asked for that conversation to happen later and that he just trust her right now. But what do you think would have happened if she had said, I'm working with this hacker organization that has been able to get me access to info I wouldn't have otherwise been able to get? What about that would have upset Oliver? Or prompted him to insist she quit? He might ask some pointed questions but again, at that time Helix hadn't even asked for anything in return. Oliver could have helped her put her guard up but even without his added warnings, would doing a favor for a group she currently placed her confidence in have been a line too far in exchange for saving Susan's life? Do we have any reason to think Oliver would have thought it was? At best he'd say be careful.

And once he was taken, Felicity probably would have made a deal even if she didn't mostly trust them.

I'm sure there will be stuff down the road to actually rap her over the knuckles for but right now it's pretty low level stuff.