How to block pg_stat_reset() statement in DB
Mutilating PostgreSQL would not be a good idea, so go and fix your application.

One thing that stands out here is that pg_stat_reset can only be executed by a superuser, so either you have a SECURITY DEFINER function that allows your application to call it (in which case you could simply change that function) or you are running your application as superuser, in which case you have bigger problems than performance issues.

Never, ever, run an application as superuser. It is never necessary, and it is an immense security problem.