TCAS is a last resort tool, nothing more, nothing less.
If you use it correctly you're fine, if you don't, you're either lucky (like the DC10 and B747 crews over Japan on 31 January 2001, which missed each other by an estimated 60 meters, after, and this is very interesting, one of the crews decided to follow ATC instruction instead of TCAS) or you're not (like over Überlingen).
Fact is, if TCAS had not existed on 1 July 2002, there wouldn't have been a collision (the 757 would have maintained level, the TU154 would have flown underneath in descent as instructed).
So, since TCAS did exist, what would be the conclusion...