Exactly right. We tackled inline editing early on, but it had a lot of hidden complexity. Tina's fields are completely customizable, and if we support inline-editing it would be more challenging to make custom fields work while overlaying the site content. There were also challenges around the inline-editing implementation being very entwined in the user's codebase.
We do hope to circle back to inline editing in the future, we just want to make sure we land on a stable solution.