I don't think you can judge the broader market by a handful of meme stocks that in aggregate represent a market cap that is tiny compared to the $31 Trillion market cap of the S&P500.
AMC and GME in particular have gotten an enormous amount of publicity on CNBC and other venues which attracts momentum traders and even hedge funds that like to speculate. Even I have traded them just for fun despite their HUGE overvaluation. They're like "casino gaming" stocks. The Reddit crowd can push them around, but they can't do that to the broader market.
The S&P500 is up 11% YTD and has a forward PE of 21, hardly frothy given this very low interest rate environment and all the money the FED has been printing .... market multiples are somewhat inflated, but justifiably so, imho. I think we'll get another 5% to 10% correction in the coming months but probably not much worse. jmho