Well my thought is to do as the OP is describing and then call it Civ VII. There are a lot of good and even brilliant ideas floating around in Civ VI. They just don't play nicely together.
The biggest thing they need to revisit are the victory conditions. Start there, and then make everything coordinate with the updated victory conditions. For marketing purposes they would need to add 3 more features. These forums alone have talked about way more than 3 that could be added, most of which would be expected to be tailored to the Industrial and later ages.
The second biggest thing they need to improve dramatically is AI. That has also been discussed to death. It does not have to be perfect, but it has to have a vision.
Since things come in threes, they need to improve the help documentation, including the details for things like reduced district pricing which has rules that it took quite a while for people here to figure out. Since district inflation is so high, and since it goes away if you prebuild a district and since this such a huge effect on civ growth, details about it and the desirability of preplacing districts is crucial. It would also help if placing a district on a forest or marsh would automatically include chopping that hex. This would be a good way to get people to see the desirability of chopping, with the help texts supporting it by providing details about just how much benefit chopping gives.
If preplacing a district caused an automatic chop, then a text box such as "Automatically chopping the woods by placing the district will reduce your build time from 15 turns to 11 turns. Do you wish to still place the district?". For the reduced district costs, a report showing how many district types have been researched and which types have reduced cost would introduce people to the concept and allow them to access the help text to get the full details.
