Millions of people pay money to wordpress developers, wordpress hosting companies, wordpress themers, wordpress plugin makers, etc. Wordpress runs half the web. I'd say building a better wordpress is a worthy goal.
A majority of those customers won't consider a "better wordpress", either because choosing wordpress is the safe option, or they are invested in the Wordpress ecosystem.
The customer looking at the LocamotiveCMS webpage has probably already decided they want a better Wordpress, and they are trying to compare between the other options available.
I'm not saying they shouldn't compare against Wordpress, but it wouldn't hurt to include a few more comparisons.
I don't think it's debatable that there are people out there familiar with WordPress who don't like it much and are looking for something else.
Whether this is 90%, 50%, or 1% of WordPress developers doesn't matter much. Even in the worst-case scenario it's still going to be a big enough niche if you're able to reach them.
