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.
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.
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.