Can you clarify what you mean by that? Sorry, I don't quite get what you mean when you say there is no such thing as a skill check.
In regards to skill checks and DCs, I have always taken the task grades as for a commoner, but I also drop them all by 5. I drop the numbers by 5 because I think an easy task for a commoner shouldn't be failed half the time for them - I could just recalibrate what I think of as "easy", but this feels more natural for me and gets the same results. A very easy task is one that a commoner would find very easy - like walking across the log that has been laid across the creek. I wouldn't even ask a commoner for a check on that unless they were impaired in some way. Moderate being a 50/50 shot for a commoner seems more like it - based on my life experience, I would put throwing an axe and having it stick in a stump would be a moderate athletics check. A given commoner makes that a coin flip. A character with proficiency in athletics, a PB of 3, and a strength of 16 gets that down to hitting doing it about twice as often. If you have proficiency, strength of 20, and a PB of 6, you'll hit that every time without fail.
For the statement about having them change for anything other than the bonuses being so high no roll is needed, that's how I do it and how everyone I know does it. I know BG3 has some things that changes based on the class, but it's not something I would do in my games. If I have decided that it takes a 10 to stick that axe in that stump, then the barbarian with a +7 is going to have to make the roll (I am assuming that there is some reason to do this, like they are gambling on who can stick the most axes). I have never found that to be an issue. I think the skill system works just fine, as do all of the players in my games. We set reasonable DCs, we don't roll for things that there is no reason to roll, and DCs are in no way affected by character levels.