A stable environment like a game where the rules are exactly the same every time it is played? I'm kidding but only a little.
For real though all the things you bring up are pretty valid, although some of them have been accounted for more than I think you know. For example something like the amount the team has the ball is frequently included when showing how many tackles and interceptions defenders and defensive midfielders make.
The part about figuring out a crap team vs a good team is also a fair thing to worry about, but it is pretty easy to adjust for mentally. And the gap tends to not be as outrageous as you'd think. For example DCL and Richarlison are competitive with the RS players despite the RS being the clearly superior team. The only team in the PL that sets itself apart to the point of needing to be taken with a grain of salt in an attacking sense is City since Pep took over.
Some of the things aren't really the job of the stats to decode. They're supposed to be a snapshot of what a player does in games. An answer to why or why not isn't really what they are there for. If as you said a player is struggling to fit in, the stats will show him just struggling, and the job of the person looking at the stats is to try and figure out why and make decisions on it.
You say OPTA is laughing but the truth is the RS use data extensively and are running away with the league. Juve use it, City use it and I'm sure other successful sides do too. It isn't meant to make every decision, but it is a useful tool.
Lastly, I do enjoy that you started this by telling me I shouldn't assume people on here don't like stats and then proceeded to explain how you don't think they hold water at all! lol
