Any filter immediately becomes a tool to limit the number of voters for the opposition.
We already have arguments over what should be considered a felony , gerrymandering county lines, etc.
Seems like requiring a certain level of education would just incentivize more attacks on public education
In an ideal world, anyone who would be affected by a policy (directly or indirectly) should be allowed to have a say in the policy.
Citizenship seems to be a "good enough" bar for letting people in this country vote on matters of this country.
And as I pointed out, any filter, including citizenship, is turned into a way remove voters who should otherwise have a say.