> I routinely have 50+ tabs open

For what it's worth, I've been known to have 300+ tabs open all in separate windows (I just forget about them and they tend to accumulate), and for the most part it handled it just fine (it did use quite a lot of RAM, of course.) That was on an i7 7700k with 32GB of RAM.

I remember being quite impressed indeed.

Genuine thought: maybe it's the separate windows?