Interesting. I routinely have 100's of tabs open on a 10+ year old thinkbook with 16G in it (they were only sold with 8 at the time but replacing the two 4G modules with 8G modules worked, 16G does not seem to work).
Firefox has an about:performance gizmo that can tell you which tabs are misbehaving, this has already led to me blacklisting some sites completely, others just to close when not in use. Especially image carrousels can be very resource hungry.
modern browsers don't really keep hundreds of tabs open, they just keep a place holder and then return the memory back to the system as resources get low. I'm not sure why people think a browser can keep 100s of webpages open when modern webpages (tabs) often use 100MB->1GB of memory.
1 or 2 GB of RAM? Yeah, that would've been the problem. Old CPUs can handle more than people think but there's absolutely no getting away from modern memory demands.
Yeah. 8GB of ram is pretty much the minimum usable amount these days. If you can get 8GB into an older machine (with an SSD), then it should work fine.
Firefox has an about:performance gizmo that can tell you which tabs are misbehaving, this has already led to me blacklisting some sites completely, others just to close when not in use. Especially image carrousels can be very resource hungry.