Over time, only very few people will buy such pictures and NFT's will get very hard to sell because nobody wants to buy old NFT's in a few years. Why should someone still pay high prices for such pictures?
I really don't know if NFT is a good investment and buying NFT's right now looks very high risk.
I agree with you that people should do a lot of research into NFTs before buying them, so they understand what they are getting themselves into. NFTs are not Crypto currencies which you can buy and just sell in a second on a exchange. Like you said, there is a lot of risk involved, but this risk doesn't mean it's not worth it to get into NFTs. Rather than looking at NFTs as a some crypto project, I would look at NFTs as art. When buying paintings or other form of art, the market doesn't move very fast. It takes time to match the buyer and seller and the price is very subjective. Also, everybody can buy a fake painting and put it up at home, but there is only 1 original. Same goes for the NFT, everybody can just copy&paste it, but there is only 1 person who actually owns it. As for any investment, we need be aware of the risk involved and there is no guarantee to make a profit.