I would go as far as saying that PHP has developed into a very good OOP programming language in the past years (from C with dollar signs to something more Java like). Frameworks like Laravel and their ecosystems are actively using modern PHP and utilising the newest PSR standards.

The issue is how WordPress seems to be stuck in the ways of the mid-2000's. You can be a "senior full stack" developer in the WordPress ecosystem but you'll hit a wall once you start applying for more general PHP roles as everything from the standard coding style to how classes and namespaces are used are worlds apart.