The bulk of the Mastering Emacs blog is a decade old at this point, but its philosophy and the information it provides is still very relevant for any graybeard wanting to get up to date.
I'm a pretty conservative emacs user, partly because I don't want to spend time tinkering to get things to work consistently across Windows, ubuntu, and mac os -- all of which I use daily. My most "modern" adoption is probably using lsp and eglot with various language modes, notably golang and rust.
Should I consider adding tree-sitter into the mix?
Nah. It's great that they're making it less of a hassle to use, but it's still going to be more of a hassle than just using the plain regex-based modes, and treesitter in itself doesn't really make much of an improvement if you already have working syntax highlighting for some mode.
The main exception is if you want to program in a language that only has a treesitter-mode, or I suppose if the regular mode has quite buggy syntax highlighting / the ts-mode has much better features.
(There are also fancy minor mode packages like combobulate that make special use of treesitter, but that's tinkering territory.)