You're pretty much spot on with the assessment of a Core 2 Duo being needed. My dad was running a Core 2 Quad as his daily driver until like 6 months ago and he really ran the piss out of it -- scanning, printing, watching videos and web browsing, loading up and reviewing 100-200 page documents, and weeky or more Zoom conferences. Running Zoom or playing youtube vids was taking 200% CPU time; and indeed, I ended up inheriting 2 Core 2 Duos and they would just keep up playing those vids for the most part. (Due to high risk of the 18 year old Dell eventually blowing caps or having some other catastrophic failure, we replaced it with a Coffee Lake system that gets about 20x the performance.)
I will note, this isn't a fault of code bloat or something. It's a matter of most videos (Youtube and otherwise) now being H.264 or H.265, where even 5-10 years ago they were MPEG-4. H.264 and H.265 are much more CPU-intensive to decode; and of course some of these older systems could use the GPU (or occasionally a dedicated decoder) to decode MPEG-2 and MPEG-4 but will have to use CPU decoding for H.264 and H.265 videos.