I'm working for a small company on something like a new PHP environment for future projects. I'd like to cram in as much modernization and automization as possible (while I can).
The thing is, I always come across solutions that require Node.js (Grunt, Autoprefixer, ...). None of our customer's hosting providers support Node.js (not even our own managed server). Most of the time I don't even have shell access.
I come across npm this and npm that so often, almost as if it's some always available quasistandard. Do I have some misunderstanding here – or is this simply only usable by people hosting their projects on their own servers? Am I just out of luck if I have to support a wide range of (sometimes questionable) shared hosting providers?
Comparing most PHP applications and most Node.js applications is apples and oranges.
Most PHP applications are fairly self-contained and intended to be used with web servers and a mostly stock PHP configuration. Most Node.js applications have a ton of NPM dependencies that need to be installed, and while HTTP is used to connect between the web server and the Node.js application, it isn't always clear what port that will be on. Plus, the Node.js application may require extra configuration, command line parameters, etc. Some hosting for Node.js is smart enough to look at the package.json file (Elastic Beanstalk for example) and figure out how to start your Node.js application.
These days you will find PHP going the same way. A lot of software is built with Composer packages that must be set up and installed. You won't find many folks getting that working on shared hosting either. Many Node.js applications have nothing to do with the web or web servers. That is increasingly becoming the case with PHP as well, but you won't find shared hosting for PHP applications.
Basically, you're looking at two entirely different ecosystems.
I think that your company needs to realize that you're sacrificing an awful lot just to stay compatible with cheap crappy shared hosting. These days you can get a $5/mo. VPS to run whatever you want, and that's often the same price as your shared hosting. Why waste time and resources while building a substandard application if you can pay $10 more a year and do what you want/need to do?
Use the technologies that you need to get the job done. If what you can do works fine in a normal PHP web application framework, then use that. If you need to build a persistent server application and feel that Node.js is right for you, use that.