We did have a watermaker then and we don't have a watermaker now, but we might get a watermaker again, but for very specific reasons, that would not be commonplace among cruisers.
The point though is that I would never say that a watermaker is/isn't appropriate for serious cruising. The answer depends on the cruiser.
You said originally that "I don't think you can seriously cruise with one" (air floor dinghy). What you meant to say is that "I don't think I can seriously cruise with one". For you a tender is an extension of your cruising enjoyment and there is nothing wrong with that. For many others, as indicated by the responses a tender serves more simple purposes.
I'm not advocating simplicity (although I tend that way personally), I'm advocating against believing something is a need when it really just a want. There are very few essentials for cruising.
It might be a safe assumption that someone on a 26 footer has a very different idea of cruising than you had, on your boat, that was more than twice as big. Maybe.