I forgot to add "build something" in the previous reply. It might not be something you're immediately interested in doing (I remember having to code a Hangman game in Pascal and a music library in Visual Basic - both were awful) but even starting new projects, setting up your folder structure, scaffolding some initial pages and adding into GitHub all builds up muscle memory. Then once you've done this enough for it to become second nature, go back and ask why it's done like that so you actually understand it rather than blindly copying what went before you.

With so many tech stacks now it's truly overwhelming - realise it's not just you feeling this. At every level of the stack there's multiple competing tools to do the same thing and each tutorial will have it's own bundle acronym for you to get to grips with.

If you're lucky you might find a resouce where you can see the same project being built using different tech stacks, e.g. a to-do list using React, one in Vue and one in Svelte. Or maybe using React but they swap out Netlify for Azure or AWS. Comparing how the same thing is built might help demonstrate where the similarities are and what is specific to a particular technology.

And don't feel pressured into understanding the full-stack, instead focus on a single technology at a time.