The decline in frontend engineering jobs matches my personal impression from the past year. Smaller companies can do a lot with vibe coding alone, while larger companies can multiply their FE team productivity without making any new hires.
Frontend code can be very repetitive / labour intensive, I bet that has made this more attainable than for other layers in the stack. Most mistakes in UI code are also easily corrected and have a very tiny impact radius.
Yeah, I've found LLMs to be pretty decent at frontend stuff.
I got a new job recently and my main task has been overhauling a Claude generated app into something functional. The backend is an unsalvageable disaster, but the frontend is actually pretty good. Which is great for me because I suck at UIs.
I think if you have a solid backend already in place, an LLM can produce a pretty functional frontend with far less effort to fix up.