A couple of points to add -
1 - Anyone can make custom components for others to use. But the community cannot create a new Anvil Editor or do a complete backend redesign or implement all these really useful features. I think the entire community will rather prefer Anvil to work on more such features than implement components that already exists as third party.
2 - The more components you add to Anvil, the more will be the base size of Anvil Apps. Since Anvil Apps are already SPA, minimising the loading time is quite important. And if an app doesn’t even use those components, that will be a waste of resources.
With all that being said, I will rather suggest Anvil to do more improvements to custom components and their discovery.