Why the Exchanging gadget doesn't work anymore with cactus when it was working in the previous versions ?

It was disabled intentionally because it was better than any mining tool. You should still be able to use it with blocks that don't break as soon as they're placed

Building Gadgets was updated and part of that involved blacklisting blocks that break on place and could be used as a strip-mining tool (though they didn't catch all cases, so it's still possible generally speaking).

You should also be able to plant rows of cactus using EffortlessBuilding, which does not require any tool, if that's what you're trying to do.

Exa's right; I didn't disable cactuses specifically - if they stopped working, it's BG's doing.