Wow, what a great generalization.
What many players don't realize is that they don't have to practice with the best player in the club in order to improve. I'd be the first to admit that it is fun to play with the best players in a club, and blasting a loop past them during a 15 minute practice match gives you something to brag about, but does not help you improve as much, as say, as 15 minutes of multiball or 3rd ball attack or any other shot combination practice with a player of your level. Just my two cents.
P.S.: Also don't forget that these "highest level players" are probably even more driven to improve than you are, and want to get the best bang for the buck during their on table time.
you are sort of assuming that the new player would have low level.
the problem is more when the new player has high level, at least higher than say 80% of the players in the club.
since there is no "coach" or "structure" in training he is just put to play with any random player.
he eventually gets bored and leaves.
I started playing late, at mid 20's.
fortunately where I started there is more structure in training for everybody, no matter if you are 12 and have ittf projection or if you are 70.
if I had been in london I would probably still be playing with a premade and wouldn't know how to loop.
as for whether my opinion is a generalization, I've been to 6 or more clubs in london and they all share the same basic structure, which is basically play with whoever you can wherever you can doing whatever drill you can or matches.
the most organized attempt is shouting "change" and forcing players to move to other table or playing the game called "top table".