99% of people don't subsequently edit photos in photoshop; Google's tools are adequate. You're in the 1% who are power users, and so might find the mainstream solution inadequate. For that reason, software like Lightroom exists.
A large majority of users [1] take photos with their phones, upload a select few on social media, maybe with some basic filters/edits, and forget about the rest.
Google Photos is designed for that use case, and not for the 1% power users.
[1] No data to back this up, just my two cents.