Today, it costs the same to transact 1000 bitcoin or 0.01 bitcoin, since you have no way to tell which input is actual spending and which input is the change. So the fee is not percentage based but per transaction based

This is a feature by design. It is similar to airline ticket price must be the same for everyone, because it must allow poorest people to travel, so it must drop the ticket price to the same level as bus or subway

As a result, more and more rich people will love to use bitcoin since the fee is almost non-existing for them, and this will cause the major user group to be middle class and above. Then when the user base largely consists of these rich people, then you can not support those developing countries with extremely low income because these rich users will control majority of the infrastructure of the whole bitcoin ecosystem