Maybe if the creation of new states (only) required a petition (with a suitable threshold) followed by a referendum rather than needing the explicit consent of both the states and Congress, I could see there being a lot more states, which have popular local support. Similarly, this could be used if areas wanted to leave one state and join another.
It would also encourage states to keep their voters happy, lest they vote to leave. However, it may be subject to corruption and exploitation. Maybe the people in power might encourage groups they don't like to secede, to avoid having to enact reforms they otherwise would oppose. For example, white supremacists might encourage ethnic minorities to vote to form a new state, thus removing what they would claim to be [insert dog-whistle here], or conservative groups secretly funding a break-away liberal/socialist state. Imagine gerrymandering the states themselves.