Zotero is not just a front-end to BibTeX. Here are some things I like about Zotero off the top of my head:

Zotero integrates well with various online services. This I think is Zotero's most valuable feature. The simple fact is that not everything exports BibTeX. Can you get a library catalog to export BibTeX? Perhaps in CS, most publications provide good BibTeX, but a lot of journals I (a mechanical engineer) deal with don't provide BibTeX at all to my knowledge. But I can simply press a button in Firefox and import the bibliographic data embedded in the web page into Zotero. (No, Google Scholar is not a good solution here because it's frequently inaccurate and incomplete.)

I'm a technical guy who can handle BibTeX fine, but I still prefer the Zotero UI over using BibTeX files in a text editor and shell, even if I'm only generating BibTeX files.

The author discusses using non-standard fields like keywords to store extra data. I would recommend that to store additional context about the document. Zotero can store even more than that, including web pages, files, and additional notes. I like that Zotero saves a snapshot of the journal article web page in most instances. Journals sometimes do go offline, so it can be nice to have the web page. I often have detailed notes about particular documents in notes in Zotero. Yes, you can do that with BibTeX, but I could see the extra fields cluttering the BibTeX file. (Contrary to what the author states, the note field probably should not be used as they describe because it's printed in some/most? bibliography styles.)

The search in Zotero is more powerful than grep. Try returning bibliographic entries where one field contains X and another field contains Y. I think you can probably come up with a grep solution for that, but it's so convoluted that it's probably never used in practice. You could use a BibTeX searching program like biblook to get around this problem.

Don't get me wrong. Zotero is far from perfect. It can be slow, and at this point I would prefer a TUI reference manager. But overall, it's the best option I've tried.