I have worked with people who make same claims as you resulting in us spending endless hours doing preparing for a scale that never happened.
Guess what our client felt about that invoice?
It's a pseudo problem, a theoretical problem, something that can be solved even though it might not be as elegant as the purists would like it to be. But it can be solved if it has to. Most often it doesn't.
That isn't a "pseudo problem".
Popularity is a bad, bad metric of a tool's quality.
Yours or mine definition of quality is of no importance to this discussion.
Some people just scratch the itches they have, right now, not the itches their expertise makes them think they should have, or the likes of Google or Facebook make them think they might have in the future.
And that is fine. Nobody is telling anyone to use PHP for their huge project, right? So why tell people they shouldn't use PHP for their mortal ones? Because at some point, down the road... can't we cross that bridge when we come to it?
No, and that's the problem. Nothing gets rewritten, it gets hacked on. PHP makes hacking on things, past a really low bar, really hard given what you get out of it. And the early benefit washes out pretty quick once you spend more than a couple days on a project. Setting up Play 2 (or Rails, or Django) is going to take me maybe five minutes longer than rolling up a project skeleton with Composer and I immediately start reaping the benefits of a sane environment. It's probably going to take me less time to be functional with any of the above than Symfony2, and I'm not inexperienced with it.
You pick your poison on day one. PHP's poison is bad for probably the 50% case, really bad for the 25% case, okay to good for the 10-25% case.
(Wordpress is not part of the last one. Neither is Drupal. I don't run either on any system I need to be able to trust. Even with FPM it's too much of a pain in the ass for the benefit I get from it.)
"It's easy to start with" is only a virtue if that doesn't come with "it turns into a tire fire a year later".