Easier and harder. The point is that we were even OLDER schismatics, the essential differences between protestants and Catholics date back to the councils from Trent onwards. SSPX is just a schism over the most recent council.
So they aren’t really ‘protestants’ per se, but there is no difference in their rejection of Vatican II as from the rejection of Trent.
For us to ‘climb over the fence’, we had to first admit that we were wrong and then start tackling the later councils. This is the hard part. Fellay et al aren’t at the point where they are willing to admit that they have it wrong.
Protestants rebelled before Trent, which only restated and did not contradict previous doctrine. Vatican II contradicts Trent and many other Church councils and papal encyclicals. Deal with it.