Mearls' example was wanting to play a dwarven smith wielding a warhammer.
And that there are several mechanics that 2024/5E inserts that get in the way of that fantasy.
- Want to play a smith? Well, you should play a farmer instead, because they get a better origin feat
- Hit someone with a warhammer, well you're pushing them away! But what if I want to hit them in the leg and stop them getting away... well you should have used a different weapon.
That warhammers get push is arbitrary. There are several weapon mastery properties that you could make a case to give to hammers. But, because Wizards wants to distinguish weapons and make martial classes more complex, they settled on the warhammer getting push.
And while that works for the mindset of "choose the best mechanics to build your character", it's a distinct difference to "choose a concept and see it realised in the game".
Not that 5E is flawless in that regard, either, but 2024 takes it further towards a mechanics-first game.