The "slow" here is very relative.

Yes, you can't push Discord -levels of messages with a GC language (like their famous "we moved from Go to Rust" post told us all).

But you're not going to be at those levels any time soon, GC pauses are just fine in a good 99.99% of cases.

This kind of thinking is a type of premature optimization, you skip whole categories of technology (garbage collection) because you "feel" it's slow based on what you read about an edge case. =)