It's more a feeling (as strange as it sounds), but off the top of my head, 1. Relay's documentation is not good enough. There were points where major features

It's more a feeling (as strange as it sounds), but off the top of my head, 1. Relay's documentation is not good enough. There were points where major features were never mentioned anywhere except for a random keyword thrown inside an example. You had no idea what it did and how. Other times you have a basic feature that should be working but isn't, and made very hard to try different things because of the vagueness of the docs. This is getting better, but not quick enough. It's not their focus, I believe. 2. It's clear from their migrations from Classic to Modern and their efforts in evolving the library that their focus is on making Relay what Facebook needs, not what might help a larger community. See 1. This is their right and their choice, but it means it makes it less suitable for my company's usage. 3. Relay imposes certain additional constraints both on the client and the server (and their schema) that might not be needed or desired. Relay uses a super-standard of GraphQL of sorts, with its own flavor of requirements. I'd rather have more freedom/adopt a more global standard with just GraphQL itself, and just have basic guidances. It can work and it does. But there's too many sore spots that I feel are greater and more numerous than what I've come to expect. Hence why I think Apollo has a better direction going forward.