Or find a stadium somewhere in the East Bay with a base of A's fans...
They proposed Fremont 15 years ago, which is still Alameda County, same county as Oakland, but much closer to the tech industry in the South Bay, San Jose and Silicon Valley. Fell apart. Land costs now would be prohibitive and it doesn't have the infrastructure to support it.
The rest of the East Bay is mountains, NIMBYs, super expensive land, or anti-development wokesters and hippies. The East Bay also has a ton of Giants fans, it's not like Orange County where the Angels have a clear advantage over the Dodgers. Wealthy parts of the East Bay like Walnut Creek, Danville, and Orinda are all Giants country in spite of being closer to Oakland.
Most viable spot in Oakland is the Colosseum site, but the neighborhood has deteriorated and even the fast food places nearby have started to close. The only In-N-Out in company history to close is near the Colosseum, and shut down earlier this year.
The root of the problem is Vegas doesn't really want them, and Salt Lake makes a lot more sense. It has no NFL competition like Vegas, and would welcome any team, whereas the feeling in Vegas is they're getting someone else's team. But baseball has a thing about Vegas and they got $350 million from the state. If they went to Salt Lake they wouldn't have the heat issues, and there's a AAA park to play in so they wouldn't have to move cities again. But MLB has no idea what they're doing with this.