One thing I'll throw out there is while there are rare cases where a solo dev really does everything themselves, when you see a really ambitious looking result from a supposedly solo dev, it's very likely they either contracted things out, bought/found assets, or had on and off help from people. It's only solo in the sense it's their vision and they get to put things together/make all the final calls on the game.
Making stuff solo is hard. I'm doing it right now and I'm purposely trying to use a lot of stock assets for art and music because the game alone is already a massive task by itself. Don't be afraid to use what's out there. If your game feels good to play most people will never worry about whether you hand built every blade of grass. In other words, go for as small a scope as you can, and don't be afraid to cut corners.
People like that really aren't fair, are they? Save some talent for the rest of us. π
It's worth noting the dude worked his ass off and had financial support to pay living expenses from his partner:
Not diminishing his accomplishments at all, but I think it's always good to compare effort to effort, resources to resources, rather than simply team size. Most people can't spend 4 years with that pace without investment backing.