Part of the trouble is certainly underpowered hardware, because a lot of sites have videos that run automatically. Even, or especially, big "reputable" sites, plus or minus the assault on your psyche and your bandwidth of playing a video without your by-your-leave. Or by your command. Compounding the problem, less and less of it is Flash, which you can at least disable. The modern thing is video and audio players built into the browser.

But there are probably a couple more things going on.

In answer to your question "am I missing something obvious?", yes, ER, you didn't mention what browser you're using. Matters, because I've been experiencing this thing with Firefox where it periodically becomes unresponsive, sometimes for minutes at a time. White overlay over the page, the twirling timer cursor...ring any bells? I did a quick google of something like "firefox freeze", and there seems to be a lot of it going around, but the proposed fixes were too esoteric, and I wanted time to investigate further.

And then there's the connection to third-parties. Poor page design can allow the FaceSpace and Tweeter and all the other "social media" (read: Titans of surveillance capitalism) buttons and badges. Same with the invisible bugs like Google Analytics. With all that stuff, it needs to be at the end of the page so that if it loads slowly, or not at all, it doesn't hang up loading the page. When that crap goes bad, pages hang.

Sounds like you might be enjoying a trifecta, ER. I think you need a new computer.

Don't feel bad, you're not alone. In part because of the same experience I'm having, I'm thinking about buying a new box. In the last few years I've invested in a lot of USB peripherals, so I think that this time, instead of the big desktop or floor mounted kitchen sink boxes, I'll get one of the new miniature boxes, aka "NUC". Small box like an external drive, just the basic guts: CPU and memory, solid state drive, display, wi-fi, bluetooth for peripherals. And lots of USB ports, so you can just plug in the expansions instead of opening the damn box and plugging in a card or mounting a drive. Pretty much recapitulates the epitome of component stereo.

Funny story: I was talking to my Dad, the venerable Attila the Republican, venerating close on to 90 years, and he started complaining that they don't make web sites like they used to. Seriously, the Net's been around that long, that almost-nonagenarians remember when it had a Good Old Days.

Hang in there ER, upgrade your box, and the Web will be young again.