I expect GME to crash and burn. I was going to change jobs at some point, in which case my traditional 401K funds will just disappear because they are not vested. If I happen to win the blue moon GME lottery I'll just stay a bit longer to vest the winnings. In my specific situation it's essentially buying memes with someone else's money at zero downside.
As for BTC, I don't use Roth 401K/IRAs as a retirement vehicle. I use it as legal tax avoidance on a very specific high-risk part of my portfolio that is tax-inefficient if it wins. Given the shitty 401K dollar limits I'm not going to put a cent of it toward stuff that's already tax-efficient if I have tax-inefficient stuff outside that can be swapped in.
The vast majority of my net worth is {municipal bonds, index funds, stocks} are all held in a normal brokerage account because they are not taxed as much to begin with. That's my actual stably-growing retirement fund, and much, much larger than my 401K.
This isn't investment advice, but if you are in a job where you are maxing out your 401K but saving much more outside the 401K than inside it, I'd encourage you to consider the math of doing all your index funds outside 401K and whatever high risk plays inside 401K/IRA. You may find the math works out better that way, like I do.