I sometime use the word invested in the context of Bitcoin, but I don't really think of it as an investment. I don't know what a better word to use would be though. I think calling it gambling is needlessly antagonistic.
I don't know if I would even consider buying an NFT of a pointless thing gambling. There is a misguided expectation that just because it has a price tag it has value. The actual perceived value(as in market price) increasing reinforces that viewpoint, but it is an artifact of a pool of misguided people that has not been exhausted.
The point is, these people have an expectation of an increase in value. For most gambling there are two categories. The most skilled wins, and the House wins. There is no rising tide raising all boats. Believing that simply getting on the bandwagon of gambling will make you money is outright delusional.
'Investing' in NFTs, I feel is distinct because it relies on the sincere belief of a false premise. Participants believe that neither skill nor luck is a requirement and just being in the game is sufficient.
Coming back to Bitcoin, I think there are multiple levels of expectation based upon multiple premises. The premise that Bitcoin, one day, replaces money. I don't think you can say this is outright false, merely quite unlikely. Others believe that Bitcoin will, at least, retain it's value. This premise is on sturdier ground but also not certain.
You could think of this as skill-based form of gambling if you think that the skill is in the ability to more accurately determine the truth of the premises. That puts it in the same field as a high risk investment though.