"Premature optimization is the root of all evil" is such a famous quote. Also, apparently, often misused (or used towards whatever is convenient). Casey Muratori did a thorough exploration Better Software Conference, 2026 of where the quote came from and what it possibly (originally) meant.
Please watch the talk to understand how nuanced this can get. BUT, I also think it is quite obvious that it is not plainly "forego of any optimization before you need", it is more like "optimize the critical bits".
Without further ado, the quote:
Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%.