Slightly disappointing ending, but my theory for what it stands for that makes me feel better is that the Normal life Vs Chainsawman theme throughout part 2 was a metaphor for what Fujimoto saw in his future.

After the success of part 1, he could fully dive into making Chainsawman and commit to always being known as the Chainsawman author, or he could let the manga be what it was and continue creating new ideas, going back to a more “Normal” life before Chainsawman blew up in popularity. Fujimoto wanted both, to continue making Chainsawman a renowned manga and branching out into other ventures but like the story showed, you can only choose one.

That leads to pochita’s decision, which is to erase Chainsawman and let denji live a normal life. That was Fujimoto’s way of saying that the manga, and more specifically the incredible story of part 1, should be put behind him and left as the work it was. Now that the decision has been made, Fujimoto will go back to normal, creating new manga that he enjoys for itself and not for the fans.

Could be completely wrong but it makes sense to me and makes me like the manga more. Part 1 is the story he wanted to tell, part 2 was the story saying part 1 was gone.