People didn't somehow develop a 'fear' of cancellations. You know what changed? There's a lot more competition now. 20 years ago, I had 5 TV channels, about 3 hours a day viable for airing 'mature' rated series, the only way to watch older series was buying $100/season boxsets, and there really weren't any serialized stories that had an ending to choose from even if you did that. Picking from the handful of shows airing on TV each night was the most common practical form of entertainment. Right now I've got over 1500 completed TV series available to stream beginning to end and at least as many movies, hundreds of video games and new ones on GamePass and PS+ each month, YouTube channels, Kindle Unlimited. The amount of entertainment practically available to the average person has increased by many orders of magnitude, and that means the bar for what you spend your time on has been raised. I've got more than 30 shows in my queue that I already know have a proper ending, and I don't have time to watch, read, or play even a tenth of what I'd like to. Why would I spend my limited time starting stories that might end halfway through when I have so much I can watch that I know won't? If you went to the cinema and there were 30 movies playing that guaranteed a full runtime, would you instead buy a ticket for one that had a 70% chance of ending at a random point partway through?

Does the behavior comply with the categorical imperative? No. But this is not a situation where I think you'll ever get people behaving in a way that does. And honestly, personally, I don't care. If this consumption pattern means that shows in the format I like don't get made, then they don't get made, I'm fine with that. I wouldn't go to the cinema if 4 out of 5 movies cut out mid-sentence 30 minutes in just because I love movies that have their full story, and if the movie industry said "but we can't financially support ourselves any other way", then that's a shame, but I'm still not going to keep buying tickets. I'd rather spend my time on other entertainment. That's exactly what this is. It isn't my responsibility to keep the TV industry financially viable. If they offer me what I want I'll buy it and if they don't they don't. I'm not going to spend my time and money on stuff I don't like, simple as that. It's not fear or idiocy to behave this way, and I guarantee you have the same attitude about something else you enjoy.