I hear this take often - particularly on HN - and I think that it is well off base IME. For many small + medium sized companies, sure, this can be true. For a scaled org with 10s or even 100s of teams building UI having an internal design system aligned perfectly with brand/marketing/content/accessibility makes a ton of sense.
It's not about reinventing the wheel out of ego. It's about "We have 150 dev teams and want to make sure there's a documented way that our company is aligned upon for building things like forms for our customers". How should the company consistently apply error states? What a11y affordances are we baking into our UI? Radix and shadcn provide much of that out of the box, are they doing it in such a way that complies with our internal controls?
Maybe for some managers it's about ego and ownership above all else. Yes, those teams probably should be using MUI, or a themed Radix, or something. But those managers are going to suck no matter what.
It's not about reinventing the wheel out of ego. It's about "We have 150 dev teams and want to make sure there's a documented way that our company is aligned upon for building things like forms for our customers". How should the company consistently apply error states? What a11y affordances are we baking into our UI? Radix and shadcn provide much of that out of the box, are they doing it in such a way that complies with our internal controls?
Maybe for some managers it's about ego and ownership above all else. Yes, those teams probably should be using MUI, or a themed Radix, or something. But those managers are going to suck no matter what.