The basic software like the Intellij Community Edition is also fully open source. (And it's not actually basic at all. It's a great full featured IDE)
Basically you're only paying for their support/updates and for specific language and toolkit support, which makes sense to me. They need to pay their staff somehow.
It's not comparable to Adobe or other crappy manufacturers where you own nothing.
Basically when you buy your subscription you also get perpetual access to the current X.Y.Z version + any future bugfixes (Z). So if you stop paying next year you still have access to the version from when your started your subscription.
JetBrains might not be my friend but they don't hold anywhere near the dev tool monopoly Adobe does for artists. Know what happens if JetBrains starts to blow massive ass? I finally sit down and figure out how to get my terminal editor working with my LSP. Yeah I lose some productivity but not as much as I'd lose by using Visual Studio or fuckn Eclipse.
I think another key difference is everyone can use whatever tool they like and still work on the same codebase. They don't have proprietary file formats that lock in you and your entire team forever.
Also, doesn't the jetbrains license let you continue to use the version that was the latest as of when your license ended. It's a small difference, but also kinda huge.
It's the version from when you paid your annual subscription (or 12 monthly payments ago) plus any bugfixes.
So you buy 4.3.2 and you will always have access to 4.3.Z
2 months later they release 5.0.0. Your subscription let's you use 5.0.0. If you cancel your subscription then can go back to your perpetual version 4.3.Z
No. I know this because a couple of times my license expired, and 30 days before it does you'll just get a little warning in the IDE - or in tools like Resharper. After that it just stops working.
If you are interested there is a great repo to get you up an running on neovim without messing with anything. I got LSP support out of the box and took me less than a week to fully transition away from vscode. It's called kickstart and is maintained by one the neovim contributors. I've done minimal tweaking months later.