Hello!
I fighted long time to figure out, why perl starts so slow ... enabled debug in apachhe2 and did see 2 x grant messages - then was nothing but site did not come. After a while the deflate message appeared and after this the site was ready in browser. I wondered, because calling the site with curl was perfectly quick. Now I found out: Change "HostnameLookups On" to "HostnameLookups Off" - at least it worked for me.
You might also want to check out what kind of (dynamic) content compression algorithms are enabled in the webserver if any. It's been nearly 20 years since i used Apache (i use my own DIY webserver), so i can't give you specifics.
Especially, you want to look if "brotli" is enabled and disable it. It has, in many cases, the best compression but is awfully slow.