The whole idea of a browser as a swiss-knife internet suite (with an email client, torrent client, web server etc. all built-in) which was hailed as Opera's main strength back in the day, proved to be an evolutionary dead end - noone really followed that path, Mozilla had an enormous following, especially among geeks/superusers, and yet its SeaMonkey never gained traction, that does tell you something

I feel Opera hurted themselves by believing that this was what made their browser attractive. Probably overestimated that factor. As a user, I cared much more about whether eg. "Look into" on Amazon worked correctly (Opera - a few years ago when I used it - was the only major browser where it didn't).

Yes internet browsing still owes Opera much credit, they popularized a great many useful solutions such as mouse gestures, the product was very solid and ergonomical, I'm not questioning that. Plus it performed well on older PCs and slower bandwidths, which probably explains why it enjoyed tremendous popularity in Central and Eastern Europe (where I'm from)