> [I] found the "hjkl" navigation difficult
That's because you're doing it wrong! Hjkl are fallbacks to move a few characters, it has only a minor advantage over arrow keys are is probably not worth the effort of re-learning how to move a cursor.
I would not recommend learning that as your first vim move. Just stick to cursors for moving individual characters at first.
The real magic is in going back/forward words (b/w/e) without needing to reach for control at the edge of your keyboard, jumping to an exact point you need (f/F/t/T) if it has a unique character (like the ')' within 'if (uid == 0)'), moving between paragraphs ({/}), going to matching parens/braces/brackets (%), going to the next/previous word under the cursor (*/#), etc. This is what will make you faster, not the switching from arrows to hjkl.
And that's just cursor moving. For editing, things like S to replace the line or C to replace the rest of the line after the cursor, di) to cut the part within parentheses and p (paste) it elsewhere, repeating the previous action with dot, searching with n/N instead of a function key, all those things are what makes vim nicer as a text editor. One of the least-appreciated things that I also use a lot is filename completion with ctrl+xf (sysadmins, take note!).
But I don't recommend learning everything at once. If you know how to go into insert mode (i), how to leave insert mode (escape), and how to save a file, then you basically have the equivalent of a text editor, especially with mouse mode enabled (the default nowadays, I think). From there, learn one command every week. Takes 1 minute per week and you'll know more vim than 99% of developers within a year.
Or go a bit faster and try to learn one command every morning, or every second day perhaps. Try it for one month and see if you want to go back to standard editors. Odds are, you'll want the best of both worlds, start looking for vim key binding plugins in IDEs, and end up like me with missing vim after all because those keybind plugins are usually not so great ^^'
> mostly using Java IDEs, and lately some vscode (for go, typescript, rust)
Do you need intelligent autocompletion, debugging, and other such IDE features?
There are plugins that, so far as I know, can do a lot of what an IDE can do, but I have never bothered to set them up myself. It all seems hacky and niche, but others can tell you more if this is the type of things you're looking for. I am not a real developer myself but I write a lot of scripts (things small enough to keep a full understanding in my head) as well as documents (reports for pentests) in vim, and for that it is perfect.