IME, this problem of 100% cpu usage is not indicative of every computer.
I have clients who upgraded to Win 10 from day 1 - on AMD Semprons, Athlons, APU's, Turion's, Pentiums, Celerons, Core2 Duo, Core2 Quad, Centrino, AMD Phenom, and everything else in between, both 32bit and 64bit.
Probably 90% of them are still using the same old spinning HDD that the computer was built with, whether that was the 5400rpm or 7200rpm drive the unit came with.
Most are also using only 2~ 4 gb of ram as well. In a lot of cases that ram is 2 (or 4) x 512gb, 4 x 1gb modules, 2 x 2gb modules etc for desktop and 2 x 1gb or 2 x 2 gb or 1 single 4gb ram in laptops.
I've got clients running Win 10 on AMD E Series laptops with 2 gb ram and not complaining about speed.
In fact I have a client with an ASUS EeePC with a 500gb spinner, 1 gb ram and Atom CPU. It runs fine.
NOT ALL (if any) of these (older) systems are affected. The problem with 100% cpu usage seems to be on newer systems and laptops.
Again, probably 90% of these systems run perfectly ok and seem quite snappy when being used for their intended purpose.