I question the conclusion that dating is bad because breaking up is unpleasant. There are, after all, many unpleasant things that are, in fact, good for us in the long run. For instance, breaking up with someone (or being broken up with) can be an important lesson in how to handle the inevitable situations that arise in human relationships when you do have to do something that someone else will not like.

Now, I have my reservations about the kind of monogamy many folks practice in our culture anyway, but even the serial monogamy of dating can serve a purpose. It need not be a matter of "we're exclusive until we're not" - presumably, the value of monogamy is at least partially tied up in the fact that one can only have so many relationships of a certain level of intensity at a time. My relationship with this person here may be consuming enough that I could not devote the appropriate time and attention to someone else expecting the same kind of relationship - but that would not mean that the focus would be irrational, nor that it would be irrational for me to shift that focus if I decided it would be better to pursue such a relationship with someone else.

I actually think the idea of replacing romantic dating with some non-romantic analogue is a misguided reform - there are aspects of romantic and sexual relationships that are distinctive, and the sort of relationship you have with someone when it is neither (partially or wholly) exclusivistic nor romantic/sexual is not always an adequate preparation for what a romantic relationship with that person (or any person) would be like.