I typically don’t use the “indie” label, because unfortunately “indie” is one of those ‘I know it when I see it’ sort of qualities.
In an industry that has demographics with high hostility towards the establishment obviously there are games made by studios to try and capture the independent spirit, and even though they may not be successful in doing so, they still hold the title of ‘indie’.
The single Indie tag is hard to compare among games sometimes, There are games like Spelunky, created by one person essentially and started off as a freeware, and there are games like Forgotton Anne, which has a 15 person development team, and then published through Square Enix. I use Spelunky because of how successful it is as an example of one that really made it. But there are countless others that don’t make it, after years of development by 1-2 people and lots of delays, etc. Then there are also games like The Official GamingTaylor Game, which was made in an imitation for one of those asset-flips (default settings, short creation time), and I am just waiting for this to actually release to see if it goes anywhere, since he is such a prolific personality.