You want to invent a road use tax which applies evenly to EV and ICE?
Tax the tires.
Every tax policy has advantages and disadvantages. Taxing tires would be a cool idea if it were easier to enforce or generated more revenue or something, but it doesn't. Tire taxes have been tried before but it went out of favor because manufacturer's made tires with poor traction just to have them last longer, and people started running tires until they were bald because they were super expensive. Tires are a safety item, so taxing them is a bad idea unless you have whole apparatus to audit the tire stores and vehicle inspections etc. Of course if you have that apparatus, you might as well just use it to enforce a simple tax on mileage or whatever, so there is no advantage.
In tax policy, you generally want to tax the least distortionary thing. You might also want to tax something that has a low administrative burden. Usually this is the thing with the least elastic supply.
The opposite of this would be taxing something that has a very elastic supply, and has a high administrative burden. The poster child for bad taxes is tariffs. Because imports are very elastic, so as soon as you impose the tariff, the amount of revenue you could earn goes down because imports drop (sometimes that's the purpose). And it's so easy to get around tariffs by marking-down prices, bundling goods together, creatively transforming goods prices into "license fees", or outright smuggling, that the administrative burden of enforcing them is basically a worst-case scenario among taxes, and you spend all the little bit of money you might have made on a huge customs apparatus.
When you tax something that has very inelastic supply, it means your tax will not cause prices to rise that much. That's because goods in demand with an inelastic supply intrinsically tend to generate high levels of rent (i.e. they are expensive out of proportion to their production cost). So when you tax them, the price doesn't tend to go up, the tax just comes out of the high/excessive rent (i.e. the price was high already before the tax). So from the perspective of the economy, the tax had little impact, because without the tax, everyone would have had to pay more for that good anyway. Put another way, taxes on supply-constrained goods are difficult to "pass on". If it's something with absolutely fixed supply, like land, it's impossible to pass the tax on because taxing land causes the price to fall by the same amount as the tax, so the cost to acquire the land is identical regardless of the tax rate. That's why land value taxes are the so-called "perfect" tax. Because land prices are pure economic rent, any tax price gets capitalized into the land cost, and there is no difference in the cost to acquire land. Now, if you can just convince all the county's in the world to stop taxing our houses and buildings and just tax the land under them, we would all pay much lower tax bills for the same amount of revenue generated.
