Yeah. That's kinda the point of the movie - you don't know. I just leave it at that. It's what makes it a great ending to me. It never occurred to me to go back through the movie and find things that may give the Thing away or make things fit into a theory through contrivance so we can "know".
The Thing 1982 had clear production and budgetary limitations. So part of the "mystery" was built into the unknown, but part of the unknown were also aspects of things that were too expensive to film. This is the struggle of the Thing 2011, there was always SFX to be able to patch over any limitations. You could argue Indiana Jones Dial Of Destiny had the same crutch. ( I.E. if you keep throwing money at it, keep adding more SFX, you can try to bypass and run over some pretty basic storytelling principles) We don't see much of the original Alien and the original Predator because limitations in technology and SFX forced the hand of Scott and McTiernan.
I've always felt the same way about our hobby. There are times when people just can't afford the latest / hottest / newest thing. But you can still have fun in this hobby. Someone can buy a big loose lot of stuff that's six generations back, and see what you can cobble together with creativity. People can have a lot of fun doing that. Building things. Repairing things. Making due with a lot of limitations. For example, the guy in the video above made a big ass HISS tank out of cardboard, old grocery store packaging, wooden dowels and leftover clear plastic probably from household items.
New current films always have that escape hatch that exists. More SFX as spackle.
The Thing 1982 is like the original Pac Man. It succeeds because it's fundamental. The old school films we all love ( Terminator 1, Predator 1, Robocop 1, etc, etc) were compact, efficient, lean and fundamental. It's just a good story. Carpenter just wanted the audience to have a good time. He had to make more happen with less. There's a certain charm in that, a certain level of beauty to it.
It's a little terrifying to think what if Carpenter was born 50 years later, was funneled out of a woke costly school, existed only in an entitled tiny pedantic social bubble with no life experience and had designs for a personal platform and some agenda over just giving the audience something fun. ( I think I just described Simu Liu...)