A client should own their website. A website owner should be able to add site collaborators (designer).
This is how it works with Wordpress, Shopify, Squarespace, Wix to name a few. And it works very well.
As it is, If a client wants me to change design they need to share their login. Instead, I keep client sites in my account, but then if something happens to me? How do they get their site?
I would love to login to the dashboard and see sites shared with me 😍.