I'm not sure about Serge being "pretty gash" at PSG. He did well in 15/16, then he fell out with Blanc (incidentally, a manager that PSG sacked before Serge was sold to Spurs and is currently not managing anywhere) as Meunier (a player about to leave PSG) was brought in and did well. Along the way Serge called Blanc a "pussy" online and had a run-in with a racist Parisien police officer.
As you can see, he played just over half the available minutes in both those seasons.
The reason he fell out with Blanc was because he was not always getting picked, especially for the bigger games, or always at RB.
My point was, the point I responded to was someone saying he'd done well before us. He looked promising at Toulouse and got his big move to PSG, where he never really managed to nail down the first team place as his own, this despite the other options being pretty meh. This gave him the hump and ended up with him making a video calling Blanc a "faggot who sucks Ibra dick".
I don't hate Aurier, when he was at Toulouse I mooted him as a possible replacement for Walker, he reminds me a lot of Walker, good athlete, decent engine, he's probably a little bit better than Walker when he gets forward, and a bit worse at defending, but neither player is very smart and both do stupid things at times because of this. Unfortunately he's never cit this from his game.
When he cuts out the stupid stuff, he can be a pretty OK option, and the fact that we've got so many major issues all our team that need addressing, doesn't make him an urgent priority compared to say DM, LB, LCB, AM/FWD but the trouble is those fuck ups just keep coming, so we do need to be looking for someone a bit smarter soonish.