What's left? The slightly unwieldy syntax (still C-like, so close enough), and the bad reputation driven by memes.
There is no specific flaw that is a roadblock, just a ton of things you know you shouldn’t do, cases you need to guard against, and base functions we effectively banned from our codebase. I still like PHP, and just moved for unrelated reasons, but I think that’s a specificity of the language (as a side effect, good PHP devs also easily become good JS devs in my experience)
PHP 7/8 have a lot more typings, it's still optional but you can require your code to use strict typings, and you can use a static analyzer like psalm to basically recommend best practices, add a few tests and your code is pretty damn solid and passes most "smell" tests and generally won't break often or as often as something in python, ruby, go.
Mix in swoole and you went from 200 reqs/sec to 6k which is about 2k more than elixir, so really just about every issue php ever had is basically replaced by just more "mature" architecture.
If you know advanced php, and the new features/best practices etc and use good tooling then php is an awesome language.
During coffee time banter, sure, but in real performance related issues, what we face came down to query optimizing, cache management, algorithmic issues and data pre-processing.
We didn’t even hit the “let’s write this in C” moment nor debated about moving parts of the code to faster systems/libraries. I’m not saying it will never ever happen, just that ruby’s sheer speed doesn’t seem to have a practical impact other than slightly higher hosting cost perhaps.