Could it just be due to lack of hardware video decoding? The Pi3 has x264 HW acceleration and youtube started using other codecs a while ago.
and to reply to another sibling, "yt-dlp" isn't workable, this is for a senior citizen that does small motor repairs.
I got an HP elitedesk that's a few years old coming in monday to replace the RPI; hopefully that will last another 3 years before google et al decide to "optimize" again.
I would have opted for a small business-pc that is x86 based and 3-4 years old.
Big companies use percentages in places they shouldn’t and it gets them in trouble. .1% when you have a billion users is a million people you’re shitting on.
For me that might be a dozen people. Very different.