I live on a corner. My "address" is on one street, but if I walk out the side door I'm on the wrong street from what my address says.
This is resolved with standards. A building can only have one address, so in the case of a building on a corner, you have to pick one. This probably varies by country or state, but I think in many places in the US, residential houses' addresses are determined by which road the driveway enters from. I lived in a house like that years ago: the front door faced street A, but the driveway was on street B, so that was the house's address. I don't really see the problem here; it's not like the two are very far apart.
If you're coming out of a larger buildings with faces on two non-contiguous streets, and want a roboUber to pick you up, you should be able to just give it your GPS coordinates. (Also, I wouldn't be surprised if in large cities, buildings like that don't frequently have multiple street addresses that are resolvable by GPS, but I don't really know. Again, this probably varies a lot from place to place, since addressing is controlled by local government.)
How do you fix the "coordinate" problem of having ten different coordinate systems in use just in one place?
Um, the default? Almost everything is WGS-84 AFAIK. My car GPS lets me enter GPS coordinates, and it doesn't ask me for a datum. According to the Wikipedia article for WGS-84, it is the datum used by the GPS system itself, so logically that's the one you should use. Again according to the article, it's consistent worldwide to an accuracy of +- 1m. For building addresses, that's far more than sufficient resolution, esp. if you're just worried about where some robocar is going to pick you up. If you can't walk an extra 6 feet to deal with an inaccurate address, you're not going to be taking a roboUber anywhere.
(Here's one I really love. I order something online and the vendor tells me that my address doesn't exist. I've lived here for 20 years, I get mail and packages here all the time. Unfortunately, the shipping program he's using has "fixed" my address and it doesn't appear in his database, so my address doesn't exist.)
Does your address exist according to the USPS? That's the real authority there. I've seen that before, where people claim their address is such-and-such, but the USPS does not recognize that as an address and so will not deliver to it. Just because Google Maps thinks it's a real place doesn't mean the USPS does. To check, you need to go to usps.com and use their address verification tool there. If it doesn't come up there (along with a 9-digit ZIP code), then you need to contact your local postmaster and have the issue fixed. However you say you get mail there all the time (I'm assuming USPS when you say "mail"), so likely it is in there, and the vendor is using some other 3rd-party address database which is incomplete. I'm not sure what the real problem here is without more information but it sounds like your vendor has some shitty 3rd-party software. My recommendation is to go here:
and check your address. It'll correct your address if you're entering it weirdly, and will put it into the USPS's preferred standardized format (no punctuation, correct city name, etc.). Use that for your orders always. If the vendor has a problem with that, then it's the vendor's fault. Point them to the USPS's verifier if they disagree. How many vendors have a problem with this anyway? One or a lot?