I think that's actually the biggest real criticism that can reasonably be made about Wayland: they ought to have produced something like wlroots from the start.

Weston was only ever intended to be an example, and its monolithic nature meant that it wasn't particularly useful as a platform on which others could build (and this was even more true early on, before libweston).

As a result, GNOME and KDE both did their own implementations - and from that seed grew a host of complaints about things not working in one or the other, when on xorg they had worked more or less the same. The lack of a common entry point for "plumbing" also hurt, and can probably take much of the blame for the initial pain that many faced when first moving to a wayland-based DE.

But, of course, that's only obvious in retrospect. I don't think it was at all clear at the time those decisions were being made originally - in other words, it was a mistake rather than malice.