What modern game can run at 1080p/60fps on a low spec PC?

What kinda of cost are we talking about when you say "low spec"?

Honestly? 4ish years of a stadia subscription will run any game released in that time period, and also the entire back catalog of PC gaming, minus some annoyingness around early 2000s games and permissions. My $500 PC runs VR at 1.7x supersampling with zero issues, and can 1080p60hz any game at all with zero trouble.

Exactly.

Four years of a subscription you can pay month-to-month (and cancel if you're not using it) is much more doable for many people than a $500+ upfront investment in a gaming rig. Presumably you also built this yourself at that price point, which is another thing other people are not as willing to do.

For me personally, I travel a lot so I like the idea of Stadia because obviously I'm not going to travel around with a gaming rig, and you can pry my 2015 Macbook Pro from my cold, dead hands.

the free one is 1080p/30fps, not 60fps.

The free Stadia tier is 1080p at 60fps. Ctrl+F "Stadia Base" at stadia.com.