Comment by WhereIsTheTruth

A JIT is a double edged sword, it _can_ make your code faster, i remember in the early days of smartphone gaming, developers often had to manually "warm up" the JIT to prevent stutters during gameplay

It still is an issue nowadays https://discussions.unity.com/t/app-needs-warmup-first-slow-...

Similar story with the GC, it's nice to have, until it causes you problems (wich it will), so you end up having to avoid using it and instead rely on manual techniques

JIT and GC aren't the panacea people make them out to be