Ignore the experts about the stock market’s continual ascent. The point is this: There is nowhere else to put your money. Bank deposits and CDs are paying very low interest (in Europe they charge YOU to hold your money). Real estate is iffy and totally illiquid.
The only place in the world to invest money with a reasonable expectation of decent returns is in the US stock market. There will be setbacks and corrections along the way, but that fact is unlikely to change any time soon.