Capitalism ruins everything

This just mirrors what's been happening with "Indie" music and films for decades already. I don't think it's even remotely new in the gaming space either. Indie is more of a genre or even just a vibe than anything else.

A Yahtzee fan by any chance?

Agreed, I think the Single-I, Double-I, Triple-I tiers do a good job of illustrating the different budget and resources available to differently sized indie developers while still properly classifying them as "indie" because they still have full creative control and the power to set their own goals and timelines with no external strings attached to put pressure on it by investors and shareholders who don't give a fuck about anything other than money. Sometimes Triple-A developers can act with a high level of independence too, but it's always conditional and subject to change because those strings are there and they can be pulled at any time. With indie developers, that creative and developmental freedom is structurally explicit. At least until they sell out (but that's when we stop calling them indie).

Stardew Valley is an indie game with a publisher. It is not about publishing.

Unfortunately people conflate single-A games with indie games. (Probably because most indie games are also single-A games)

Remedy is definitely indie, but I'd consider them an AA studio

I think the weirder question to ask is how much publisher/investor pressure should there be for a game to no longer be considered indie. Because it seems to be that there's many publishers that exert little to no control over a game's contents, especially if the publisher is itself an indie game studio. For a while, as well, Microsoft seemed to have not applied any editorial pressure to any of the studios that they bought. So would these games (eg Ori) still be considered indie?

Then yes.

Yes. By those parameters they meet the definition of "indie".

Remedy would be considered an independent AA studio.