There are pros and some substantial cons to rotomolded construction that you may not have considered. Yes, you can throw a rock at it or play bumper boats and not worry too much - but when you have holed it, you have a big problem. When your keel wears after the 100th time you slide it up the beach, you have an issue. The problem is that repairs of this nature on poly boats are very difficult if not impossible. You're not going to fiberglass it together and the "poly-welding" that used to be possible on them is not anymore. The the new cross linked polyethylene materials they are using to build these boats today are superbly tough but do not lend themselves to heat welding or other means of repair once the plastic is solidified. So yes, they are more durable but they are less repairable. Poly constructed boats are great for businesses that intend to depreciate and eventually trash the asset after several years. I wouldn't recommend it to a sailor that intended to use it at a high frequency for a lengthy period.

The tooling for producing a rotomolded object can more expensive as well but pays for itself through high iterations of production - so not suited for small runs.

By contrast, if you wear out the keel on a fiberglass boat, it's ready to go again after few hours in the garage.

The Wave class is a terrific racing class with very tight and very even competition. I think the Wave fills a very neat niche in the industry. Personally, I've had some of my most fun moments on one and would certainly have one in my backyard if I thought I had the time to sail it. Fair, even, and exciting racing can certainly be had on any rotomolded sail boat - speed is relative. I just don't think it's going to be the wave of the future (pun not intended).