If those engines have a 3600 ELOElo, shouldn't top players have profited from it to leave Kasparov's 2851 score in 1999 far away?
No. The main effect of engines and also the internet has been to democratise chess. The top players have always had access to top level evaluation and knowledge. For lower level players that kind of knowledge, analysis, position evaluation, endgame knowledge was very difficult to acquire.
This is important because higher level players gain rating points by beating lower level players. If those lower level players are harder to beat because of increased access to the analysis and knowledge that engines and the internet provide then it actually becomes harder to reach higher levels as measured by rating.