I'm fine with old people voting because I don't think it's right to disenfranchise anyone without going down a dangerous road. There are a lot of 18 year olds who have stupid uninformed political views too but they tend more to vote the same as me so I have a less visceral reaction to stupid kids voting than stupid old people. I also think felons should vote in every state, too, because any group of people that are permanently disenfranchised becomes a group the state suddenly has interest in ignoring.
Requiring that voters be "informed" is just a dogwhistle of the conservative realization that if we made it easy for everyone to vote, then we'd never elect a single conservative again. A foundation of conservative thought is that "the people" are essentially idiots who would vote for free candy and dessert before dinner and tank the economy with free handouts, but that the "informed voter" knows best and will vote for the most "economically sensible" policies. Of course in practice the "informed voter" tends to look much more white, male, and landowning than the average person in the conservative mind, and "economically sensible" often translates to letting certain people die in exchange for higher GDP.
A maximum age for holding elected office however - that I could get behind. I don't see any reason to oppose preventing anyone over the age of 65 at time of the start of their term from holding political office, which would effectively limit the maximum age of the president to 69, senators to 71 and the house to 67. I don't think we should ever let it become a question whether or not an elected official is really still "all there" and I also don't think any politician, no matter how popular, should hold onto power for that long.