I agree at about 200B USD market cap, BTC is not too big but not too tiny either, offering VERY interesting fluctuations and dynamics for trading.
Now regarding trading crypto as CFD and getting big spreads, low leverages, huge swap rates, horrible conversion rates from BTC back to USD and other disadvantages of traditional FX brokers:
I used to expect my excellent FX broker to offer me good trading conditions and account environment to trade crypto, but was gettting the bad conditions mentioned above. It is not the broker's fault, it's just it's not their line of business. My solution was to switch to specialized crypto exchanges. I have accounts in two of these, one is a very well known and does not offer FIAT money conversion. The other one is UK-regulated, does not have huge liquidity in the order books, but I can use for SWIFT and SEPA transfer to my bank accounts.
Additional interesting note is that my FX broker converts USD to USDT, costing about 1% which is reasonable enough (while BTC USD conversion is about 5%!). Again, FX brokers are meant for FX. The same goes for crypto exchanges.
I hope this help. Once I accepted this, everything became cost-efficient on all sides.