On top of that even if a cryptocurrency manages somehow to completely level the playing field when it comes to mining hardware you still have significant differences when it comes to cost of electricity. Bitmain will stop building ASICs and start building hydroelectric dams instead.
I can't see how you can imagine a future where cryptocurrencies are successful and it's still worthwhile for individuals to mine in their basements. There's always be economies of scale that'll favor the cartels.
Beyond that it might even be possible that PoW algorithms designed to run on general purpose CPUs can end up giving more power to the cartel than an ASIC optimized algorithm because in the latter case the network consensus can decide to hard fork and change the PoW algorithm, hurting immensely the ASIC vendors and their users. That gives leverage. Similarly a new cryptocurrency or minority fork can protect itself from a 51% attack by changing the PoW algorithm, making highly-optimized mining farms unable to attack the coin (Bitcoin Gold should probably have considered that).
Meanwhile if everybody uses general-purpose server farms to mine then they can easily be repurposed to attack any small coin, making sure that the coin they favor remains dominant.