I believe BIG BANKS are prohibiting clients from using Credit Cards to buy crypto as notorious way of keeping money in the banks which will make more money for them. I agree with your point as the market is crashing small investors will sell out and big whales will buy big amount which will increase Bitcoin price, and whales will gain from it.

I am also a huge proponent of dollar cost averaging. In fact I wrote about how it saved me here https://steemit.com/cryptocurrency/@reazuliqbal/dollar-cost-averaging-as-a-savior