They don’t have that obligation to finish the story, but Half-Life 2 Episode 2 immediately retcons the ending of Half-Life 2 to give you more play in the world. Half-Life: Alyx, the entire game is a retcon of the ending of Episode 2. So to sit and claim there was nothing narratively interesting to work with and not a good direction to go in, is ridiculous because they always had a an escape hatch with the retcon.

A company that has failed with sales of Portal 2 but has plenty of operating capital to continue on, Half-Life 2 Episode 3/Half-Life 3 at the very least was a promise they made and walked back. Yes they did owe something to the fans over the last 20 years.

They were the ones who set out to outdo the previous episode and let the idea blossom into never good enough, not the fans.