If I were designing "inborn power" mechanics from a blank slate, they'd look more like the warlock than the sorcerer. And "borrowed power" wouldn't look much like the warlock at all. In fact, in a 2E-like paradigm, you could have a single low-level wizard spell that contacted a fiend willing to teach other spells at some grave cost, rather than having to dig spell scrolls out of dungeons like an honest mage.Thematically there's a niche for Sorcerers. They form a trinity with Wizard and Warlock of learned power, borrowed power, and inborn power. The big question is if there's a mechanical niche for Sorcerer that's both distinct from the other two and still robust enough to support an entire class. Evidence for that is scarcer and more conjectural.
I have no objection to the Sorcerer existing. In fact, I rather like the concept of its flavor. But there's very little history of D&D being able to deliver a Sorcerer that's not living in the shadow of the Wizard, and it doesn't have a strong enough legacy to justify keeping it around for that alone. So many you kill some sacred cows and reinvent the Sorcerer. Maybe you merge it with the Warlock and include a toggle option between inborn and patron power sources. Or maybe you just cut it. I don't exactly have a horse in that race, besides the mild annoyance of occasionally trying to play a Sorcerer and being disappointed.