My playgroup has about 8 people, but each week it is typically the same core 3-4 with others showing more sporadically. Our powerlevels since I have joined have all started to rise with players upgrading to compete, which causes others to upgrade, and so on and on. This is about the extent that it affects my deck building.
I build decks with budget in mind, I am usually aiming for the cards I purchase to be under $100 total. If it works and I like it, I do a few small upgrades to get it to a point that it has some consistency to it, after that I leave it alone and enjoy playing it. But I don't stay on a deck for too long, I end up brewing something new every couple months. I occasionally circle back to the decks I really enjoyed and invest a couple more cards into them. None of my decks will ever make it to cEDH power level (on purpose), but I never really feel underpowered in our games. I also heavily invest my deck building strategy with the commander, I want my deck to reflect the goal that my commander has set (which I think can be a hindrance to power level at times). At the end of the day, I would rather build an entirely new budget deck, then spend that money to upgrade any deck past a certain point. Building the deck is much of the enjoyment for me.
We have one player that builds higher level decks, but with politics and everyone else usually assuming he is the threat, the games are typically fair. Does he win on turn 4 occasionally, yes, but that means we get to go to the next game.