Sadly I see this all the time now, on nearly all professionally created web sites.
I'm fortunate in that I have a fast internet connection and so they whiz through, but for those with dial-up or slow broadband it can be a real problem.
You mention older machines. I remember the first car I brought over 40 years ago had drum brakes and cross-ply tires. Remember those? Things move on and such vehicles wouldn't be allowed on the roads here in the UK nowadays.
No such restriction on the internet of course, but 'things move on'. That's my 'real' answer, for what it is worth.
Mark
Has anyone noticed, or counted the instances of "script" running on these pages. It's ridiculous!! The pages load slow, when I scroll up the pages jerk, I get messages that xxx.xxxx is waiting! I run FF and installed "No Script". I was amazed at the total number of scripts running. I got 17. When I turned them off, some things wouldn't work, naturally. If I turn them back on one at a time things are better. But geez! Is all this crap needed? And every web site has between 10 and 20 or more scripts running.
Has anyone tried to run the internet on an older machine? I had a little ThinkPad running W98SE. I had to put it away!! It would not surf because of all the crap embedded in pages. Why can't someone write a page that is bare of crap and loads fast? Seriously, why not? Can someone give me an answer? For real!

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