Site gotten much slower after upgrading to v4, any tips?

After upgrading to v4 some weeks ago, some users have complained that the site has gotten much slower since. I have Op cache enabled, I also did php artisan optimize and php artisan filament:optimize

I also applied the latest server patches and restarted server

The site also did not get more popular, it's the same as the past

So not sure what else I can do to speed up the site.