I've been maxing my 401k for 4 years. Everything is in total stock market index.
So I put in around 75k. With employer matching, it's around 105K in total contributions.
That account is now worth around 140K.
I had a personal account with only 20K in it 2 years ago. I didn't add a single cent to it, yet that account is now worth more than my 401k.
401K is terrible. I think contributing up to your employer match is a good idea, but anything more is a waste. Sure, there are tax advantages, but you're restricted to diversified funds, and those are terrible investments to people who know what they're doing.
My investments in my Roth IRA and personal accounts are TSLA and bitcoin. I will be making a move into ARKG, as I believe the next parabolic industry this decade will be genomics.