You're just wrong. PSRs are widely accepted and all serious frameworks and PHP libraries implement them as needed. I haven't seen a PHP package in quite a long time that didn't implement PSR-4.
What statistics source are you using to determine the 'largest framework' here?
Even if we go back to the 2021 Jetbrains developer survey (https://www.jetbrains.com/lp/devecosystem-2021/php/) out of the 11 named frameworks/platforms people are using all but 2 of them use PSR and composer.
You keep making these assertations which frankly are coming across as absolute bollocks from someone who's stuck in the early 2000s.