You misunderstand. Before tetraethyl lead was removed from gas--in the 70s, I think?--engines were not nearly as good as they are now. My dad was doing really, really well to get 100,000 miles out of a car in the 60s and 70s; you used to see a service station attached to every single gas station, because of how much service cars needed. Now, 200,000 miles is close to the minimum that people would expect with only preventative maintenance. It's nearly unheard of for people to need to replace valves and regrind valve seat now, except for high compression, high RPM engines (esp. supersport motorcycles). But that was just normal before the mid-70s. My dad has done multiple full teardowns on engines before the 80s, replacing head gaskets, piston rings, valves, and so on. These days that's almost unheard of.

I think that the most intensive valve maintenance that I'm aware of that's common right now is cleaning carbon off for some of the direct injection engines. I know that it's an issue with Volkswagon cars, but most cars don't do DI. You'd have to check technical service bulletins (TSBs), but most cars are very trouble free compared to what you could expect prior to the 80s.

If you want a sad rabbithole, look at the cancer rates around small airports, which are often much closer to where people live.

You can absolutely get high octane ethanol-free gas; there's a place near me that sells it. I know that a lot of people with motorcycles use it, because inline four cylinder motorcycle engines tend to be high compression, and motorcycle people tend to be almost religious about not using ethanol. (Which is unnecessary; assuming your motorcycle is fuel injected, the only risk with ethanol is storage for several months at a time with a full tank of gas. If you do that, then you're going to end up with water in your gas, because ethanol is hygroscopic. As long as you keep riding regularly, or empty your tank and run the motor dry before storing it for more than a month, you'll be fine with ethanol in your gas.) I know of at least once place near-ish to me that sells 110 octane ethanol- and lead-free racing gas. Ethanol-free high octane fuels tend to be about 25-50% more expensive than fuels with ethanol.

Avgas is another story. The odds are pretty good from what I can tell that any prop airplane is going to need gas with tetraethyl lead. To me, that sounds like a good reason to remove them all from service in favor of jets, but I think that jets have a higher stall speed, which can be a problem, esp. in backwoods areas.

(Jet-a and jet-a1 are kerosene derivatives, and don't have lead.)