I definitely wouldn't use GPS as a sole indicator of someone's position for a game.
My problem was that I thought the core gameplay was really flawed: there was (there may be now, I haven't played for a while) no benefit to holding territory, only taking territory... which means you have a vested interest in letting the other team capture your portals so you can take them back. So after a while each team takes turns capturing the portal and sticking cheap and crappy level 1 resonators on it. You don't want to make the portal hard to recapture. That's not fun.
Wandering around cities looking for portals was fun, and got me to find several places in the city where I was living which I wouldn't have found otherwise. (I have since moved city. Maybe I should try it again...)
Oh and the game is divided up into seasons, you can see in the Intel screen a history of how much area your 'side' holds and has held historically in the current period.
That said, it can still get old fast. King-of-the-hill + geocaching essentially. Claim areas, lose areas, nothing lasts for long, etc. Still, it can be fun to see the opposing faction trying to make a big field to gain points before the end of a cycle and coordinating with other people in your town to knock it down before they score those points. Same goes for the opposite way.
Besides, if I wanted to talk to other humans, I wouldn't be playing a computer game! I gave up on Eve for the same reason, once I ran out of early game content and realised I'd have to join a corp to progress.
I think this is pretty common evolution for games. Games from bridge to Magic:The Gathering to softball are as much about the social elements as they are about the actual gameplay.
Which is probably why I quit; I much preferred walking around on my own, rather than trying to coordinate with people.
Oh well. It wasn't for me, and in the month or two that I played it, I did see some pretty neat stuff around the city that I hadn't before.
It's a lot harder to spoof say for example APs near you, signal strength to a cell tower, and/or IP geolocation - than a GPS signal.
If you can spoof all of that - you probably aren't interested in playing a game like ingress. You have your own more interesting game you play...
Combine that with Niantic's shift from freely giving equipment away to forcing players to "glyph hack" (repeat back a series of proprietary symbols) and casual players dropped out of the game.