I am playing on Lichess and just dropped from 700-800 range where I frequently played >800 ELO numbers back to the 600 range and in some way its also true there. I dropped down on an evening where I probably should have just stopped playing and so now I have to make my way up very concentrated against players that objectively don't develop their pieces well but somehow manage to make renegade moves that are challenging to counter...

I completely agree with you. Sometimes they absolute noob, sometimes that absolute noob you underestimated see some crazy three move tactics.

I also noticed the difference between the low level Lichess players and the Chesscom players,

The lichess players usually play normal opening, the Italian, london, sometimes the Spanish etc.

The Chesscom players just play whatever, king's Indian defence,the english, hell I've encountered some b4 shenanigans too. 1000 - 1300 Chesscom player are wild.

As someone who only recently returned to chess.com and chess in general, I’m narrowly leading in an endgame in my ongoing correspondence game against a 1000 (which might be creeping towards a draw) and somehow once beat the 1500 doggo bot, but whenever I reach the 800s in Rapid I slip back into the 700s because I only know like 3 opening lines, and it especially doesn’t help that 680-740s love experimenting with the non-e4 opening moves as white, most of which I don’t know the proper defense/punishment for as black except perhaps the e and d pawn push for Nc3 and getting in with your queen through the fortress’ unguarded diagonal for the Catalan if they play g3 first (I do know the englund, caro-kann and french as well as the 4 knights game but most of those assume the opponent is predictable enough to play e4). As white I know a bit more theory (king’s pawn, vienna, catalan and while not very effective on triple-digit players, the ballistic missile gambit).

And I haven’t yet memorized a lot of book moves so my Blitz elo is in the toilet because I keep losing on time to complete noobs