Aiding other characters in what they do is an important part of any roleplaying game--it's a team game, after all. The basic rule in Starfinder and Pathfinder First Edition is this: if you want to help someone do X, roll X as though you were doing it yourself, and if you succeed at a DC 10 (no matter what the actual difficulty is; 10 is the DC for the helper check), you give them a +2 to what they're doing. There's no risk to aiding. That lets the GM limit the potential bonus by limiting the number of helpers. In practice, GMs generally let everyone at the table help; in a typical group, with everyone trying to help, somewhere in the range of +4 to +8 isn't uncommon.

Pathfinder Second Edition makes helping a little more dramatic, but a whole lot less effective. The DC is normally 20 to add a +1 bonus to the person you're helping. If you critically succeed, you add +2, but if you critically fail, your ally gets a -1. These bonuses don't stack, so as soon as someone provides help, there's no reason for more people to try unless they can get a critical success--and if they do, there's absolutely no reason for anyone else to try. The rules, not the GM, limit the potential bonuses, and they're limited to +2. The weird thing about this is that low-level heroes--the ones who most often need help from others--are pretty actively disincentivized from trying, as 20 is a pretty high DC and there are consequences for failure. If you're a low-level character who can reliably hit a DC of 20, you're better off being the main character doing the task anyway. The aid rules make high-level characters even better at doing their high-level things; they don't help low-level characters able to do difficult low-level things.

I have a lot of dissatisfaction with the aid mechanic in Pathfinder Second Edition, so I've been looking at other game systems to see how they do it. (Being well-versed in several systems is helpful for designing games of any kind!)

Dungeons and Dragons has it easiest: if you take an action to help, the person you're aiding rolls with advantage. No need for the helper to roll anything at all. Since advantage doesn't stack, there's no benefit to having more than a single helper.

Torg Eternity is a more complicated: you get a bonus based on how many helpers you have, but that bonus isn't linear (one helper gives +1, two helpers give +2, three or four helpers gives +3, five to eight helpers gives +4, nine to thirteen helpers gives +5, etc. There's a table). If you want to help, you automatically count as a single helper. And you can be fine with that, or you can actively help better by making a check: a result of 9 or less means you don't count as a helper, 10-14 means you count as a single helper as usual, 15-19 means you count as two helpers, and 20+ means you count as three helpers. 

I find Torg Eternity to be the most satisfying, because it gives players a little agency: how much do you want to help? If you're not really confident in your ability to help, you can take the "D&D route" and just say, "I help." and leave it at that. If you are more confident, you can go the "PF2 route" and try to give better aid at the risk of not helping at all.

I would like to pull something like this into Pathfinder Second Edition with two simple additions:

* if you are committing your reaction to helping, you automatically add +1 before rolling; a critical failure thus means you don't add anything, but you don't take anything away.

* the GM can expressly decide how many aid attempts stack, instead of a default of "they don't stack."

This will absolutely make aiding more powerful, and perhaps able to overcome the orderly and bounded difficulty-by-level framework more than the designers intended. But that's not a downside to me. I feel like an RPG should have a collaborative feel, and incentivizing helping each other moves in that direction.