I understand contributing at least the amount an employer will match, and almost always much more than that. But to "max" it would be $24,500/yr which for many if feasible at all would leave little go into different investment vehicles meaning all of your money is tied behind the rules of a 401k until you can access it, or take that 10% penalty.

Maybe I'm missing something here but diversification is a pretty fundamental investment rule and I'm not sure why the advice doesn't usually follow it here. Putting everything into a "you can't touch this until you're ~55+" bucket seems like quite a risk.