Is it sad that there isn't a proper ending or finish for most of the characters? Yes.
Is it so bad that I'm going to heavily criticize the dev? No.
Simple reason is that as far as I'm concerned, PT was never a story based game. It was (in my opinion) what a sexual/porn game should be; a game with a basic yet unrealistic storyline with lots of beautiful sexual content. Didn't play for story fulfillment, played to get the required dose. Props to those who can do both sexual content and an amazing story, but I find it more frustrating when there is a story but no actual sexual content which sadly tends to be the case for story based games (something like a year worth of content, but all you've seen so far is 1 character nude out of hours of gameplay).
Besides, I'm actually thankful to Domiek for being honest enough to say that their passion for the game ran out. Also thankful that they tried to stick with the game for so long despite that. In a place where a number of creators leech money from people without putting content out for multiple months or years on end, to let us know and even bother putting a last update instead of leeching and posting false teasers for a year and then doing the same thing regardless is a step forward at least.
I'm not saying that there shouldn't be criticism for a bad ending, I'm just saying that people should also admit the good, not just the bad. Even though Domiek mentioned they don't mind criticism, but when that's all there is and all the good is ignored, I can't imagine it not being demotivating.
For what it's worth, despite having my issues with the ending, I loved the art and thoroughly enjoyed what the game had to offer.
Look forward to seeing what the dev puts out in the future!