I also had to relearn, but it turns out that for me, it is easier to see a rectangle in the square than to see the square in the rectangle. That means, if you come from a smaller format, there is still much gain even if you crop to a landscape format.
OTOH, I think there are subjects which beg for a square format and others that just do not fit well into it. I think using the whole format is good but being a slave of it is bad.
BTW, a good example that it is possible to do very good square landscapes is the book "Japan" from Michael Kenna. Maybe not everyones cup of tea, but I like it.