To be honest, yes, unless we stayed on 1.x forever, though I imagine many add-ons written for 1.0 won't work with 1.4 anyway. The transition is the same that happens with the changes within the 1.x branch, but much larger. Eventually there need to be significant changes that break compatibility; when that happens, the first number gets changed.
Because of the amount of customizability that XF offers, add-ons can hook in anywhere and do a lot of custom or unexpected things. As such, it's simply not possible to maintain the level of backwards compatibility to allow old code to work, particularly if it integrates into core code.
Just to be clear. I am on your side. I love Xenforo and want that it progresses. And for this you need these cuts. I understand that and accept that.
Yeah many add-ons written for 1.0 won't work for 1.4, but most did for 1.1 and they got adjusted. And then so on. So an adjusting was needed.
If the system would stay like it did from 1.2 to 1.3 or from 1.3 to 1.4, that would be fine. So from 1.4 to 2.0. That is ok.
But you talk about that everything will be wiped away.
Ok, then I ask for too much. I understand. But there is another solution for this. If you can't provide enough compatibility due to new structure, why don't you add many of the add-ons by default to 2.0? That would make you happy and us happy.