I blocked a bunch of those accounts and the number of rando hot girls trying to get me to follow them dropped really quickly. You may give that a try. Maybe they have some very rough algo that does attempt to stop those follow varieties that you block a lot of
probably the rando hot girls are all run by the same big bot farms, or bot farms sell suckers lists so if you are a sucker for one rando hot girl bot the others soon find out.
They're trying to simulate real accounts by following people. Blocks are likely a strong signal for anti spam. So if the spammers notice that you block bots, they won't want to burn accounts by following you, and will instead follow accounts that don't block bots.