Modern PHP is much better than most people expect. It has very little to do with the PHP4 we all grew up to dislike for its quirks and inconsistencies.
That said, I wish more software was done in PHP. And for me it makes a lot of sense regarding the Fediverse. A PHP platform I can put on my existing shared hosting and connect some (sub)domain to it and call it a day. Most smaller/meduim businesses probably have that hosting constellation already around, idling around most of the time. The entry barrier is just so much slower than spinning up a VPS or renting cloud space somewhere just to test a small instance of something. Sure it scales not as good as your average cloudplatform but for most usecases that is not the biggest concern.
Different product but I love Matomo as a Google Analytics because I can just copy the files to a clients shared hosting, connect a subdomain to it and if it uses Sqlite (also better than it’s fame!), I am done already and don’t need to create a database even.
You are right that there is a dockerfile for pretty much everything these days.
However, as an example, I am using Sabre as a CardDAV/CalDAV Server on one of my domains. There is simply no need to spin up an extra container for something simple like this. Same with Matomo for analytics in my comment above, you are just writing a better logfile essentially.
Now Kbin has much more functions than that and I would probably run that in a container as well. For smaller and leaner things, I see shared hosting still as the easier way. When you know that containers exist, you are already in an expert bubble. I would claim that many many people know how to use an FTP client from their Desktop than are able to host a container somewhere - not that I’m a fan of FTP but SCP is already more advanced for that said group I assume.