I quit tf2 in 2019 for a full two years. I've been playing for only a few months after that hiatus, and I'm already drastically better than I was before I quit. The only conceivable way I could see the "time away from tf2" argument apply is if someone has gone through irreparable damage to their mental state. Unless you quit games in general it's not like you get worst over time at videogames generally. The time between their seasons should not matter.
All this to say, the fluey team has 4 players that made 4th place in main 6s. That is literally a team that could've gone even in advanced. Would you all be okay if b4nny dropped down into main 6s to play medic? I don't care what you restrict him from, restricted to med only, the main players are literally just gonna get comms diffed. Now, take "mid advanced" players, quote, and put them in amateur division, and restrict them off 2/3rds of classes, they're still going to roll everyone. Like, I think I have a combined 100 logs on soldier and scout, the rest on demo, but of the few times I've played those other combat classes it has been with my friends in pugscrims in lower divisions such as AM or IM and it isn't hard to just DM and comms diff them even on those classes.
The fact that the fluey team is currently undefeated in AM is proof of this. It's absurd that they are allowed to be in this division.