Scott,
It all depends on the needs of the websites you build.
If you are building small websites and have very light load and traffic, small databases and also need domain and email handling - you should definitely use fantastic solutions like Plesk and cPanel to handle them all in.
However if your web sites are getting more heavy load and need more a server on their own and don’t want to be bothered by sharing the same web server and database, then you should consider docker cloud hosting.
Also note that you can just use both solutions - start small with shared hosting and keep there the regular stuff like domains and email but when the website/app/api need to scale just get it out and put it on its own server with docker. Just redirect the hostname in the dns to its ip and you are done.
You can also do combination - on the same docker server you can run indeed a few services and websites, it doesn’t have to be just one. But no more than a few otherwise you will have the same slowdown as too many sites on a shared hosting.
So docker is not a replacement of regular hosting - it is just a natural addition when you are scaling up.
Docker gives you much more control by enforcing separation of concerns that pays off when scaling up and moving more to Microservices architecture and its fit to Docker
So it is all natural evolution. And again if you have just small web sites running perfectly on shared webhosting - just stick with it! Docker will be definately an overkill there. I’m sure @JonL will agree to that
There is also another solution to have on the same host Plesk, as you probably have it now, but also install Docker in Plesk
Just as you can have Git in Plesk
Both great options to start with better publishing of your sites than just FTP. and giving you more version control and easy rollback posibilities.
I’m sure there are similar solutions to cPanel as well.
PS. Having docker for Local Development is a different story and a must to replace those WAMP/XAMP solutions.