That bugs me to. They could have just re-wrote the older code to optimize it, but no they had to do a total restart. Love the game, but this excuse it's stupid.
Yeah IMO what he should have done with the initial rebuild version is reuse his existing images instead of redoing them. Add new stuff using whatever new methods he decided on, and if he wanted to replace the old images, do that slowly as kind of a bit of an add on to whatever new development happened. So the rebuild would have started off already having as much content as the previous version and he could slowly replace the original images if he wanted to while he added new stuff.
If development speed had actually improved with the rebuild like he predicted then a full redo without reusing anything would have been fine and I don't think many would have complained if we were consistently getting bigger updates at a faster pace than before. But we're not.
I do like the game, but at current dev cycle it's going to take years before we have anything resembling a playable game rather than a tech demo.
An example of a rebuild done right IMO is LOP's rebuild of LWT. It used to be a flash game and had several expansions. First version of the rebuild came out using Renpy awhile ago and was basically just a tech demo with only about a week or 2 of playable content. It was kind of buggy and there wasn't that much to do yet but you could see their new systems and get a feel for how it would play when they got farther along.
Second version had most of the content from the full original game plus some of the expansions including some entirely new scenes, but mostly rewritten original scenes with the original images. Next version is supposed to be almost entirely caught up to the full version plus all of the expansions, and then they plan on adding a decent amount of entirely new content going forward from there.
Regardless whether you like LWT or not, THAT's how you do a rebuild IMO.