Bitcoin is the least risky of all the cryptocurrencies. It has the largest user base. It has the most widespread infrastructure. It has financial products and derivatives. Every other coin is unproven, many are mostly unheard of, and are the highest risk.
Saying every other coin is unproven is disingenuous.
Most of the coins people are purchasing today have been around less than a year and probably have less than 1% of the users of Bitcoin. They're pretty unproven.
The things you say are true, but it's also suffering the worst from transaction fees, scalability problems and has worse technology and struggles to innovate.
Scalability problems sure, bitcoin is hardly struggling to innovate though. Rootstock, Schnorr signatures, mimble Wimble. These are awesome new technologies. Every coin today would have the same scaling problem bitcoin has if they had the same user base and amount of attacks going on.
Well, some can't sell 'cause coinbase has turned off transactions.
Bitcoin actually dropped at one point from $14000 to about $10500. It has since rebounded.