Bitcoin uses a representative democracy. Mining pools are the representatives and miners vote on those representatives with their hashing power. PoW and DPoS are not comparable to our current representative democracy, because they are completely liquid democratic systems, in so far as delegates and mining pools can lose their voting shares at any point and their task as a representative are easily understood and auditable by the public.
Your last point doesn't really make sense. You can hardfork a DPoS chain...
Correct, as I clarified that DPoS can be hardforked above as well. The key difference is delegates (miners) within Bitcoin have large costs and constantly need to innovate in a competetive market where the benefit for being in that role of power isn't as good as with DPoS.
With DPoS you are king if wealthy as you can vote yourself into office and perform a profitable task that has a much higher net profit margin than mining. Essentially, with DPoS early and large stakeholders are setting themselves up to dominate not only control of the vast majority of wealth in the money supply but the voting process. With bitcoin you can own a lot of coins but if you also wanted to control a percentage of the voting process you have to give up some of your wealth to innovating ASIC technology and paying for power. So with PoW it is difficult to maintain control of both as you have to pay the salaries of pools, asic manufacturers, solar/microhydro/ and other power sources, ect...
PoW gives power to those that are willing to destroy the most resources at the lowest cost. It is not economically rational and tends more to centralization than PoS systems.