While the smaller Hobies and the related sail for them don't create true sailboats as we think of them
not sure I agree with this contention... ...what is a "true sailboat"?!
My $0.02 is that a Hobie kayak equipped with a sail performs exactly
like any other sailing boat with a fixed mast(s) but on a "micro" scale.
Sure sailing kayaks are smaller and in most cases simpler (though you can mod them easily and cheaply to increase the complexity and similarity to more complex sail boats if you want). Apart from that IMO there's no difference except in speed/power, wind range, seaworthiness and pointing ability (which factors apply to every sailboat so Hobies are no different here either).
When I need a sailing fix I couldn't really care whether I am on a Hobie a "proper" yacht - the experience is basically identical. In fact the Hobie is SOOO much easier to set up and so much more engaging to sail than my other sailboats (2) that I rarely if ever bother to go out in the other ones... (note to self: sell boats because they simply don't get used enough). I have had other engaging sailing experiences (e.g. on Steinlager 2) but at far greater cost/commitment and with far less availability.
That said I am lucky to live in a place where the conditions are frequently ideal for a sailing kayak - it might be a lot less usable and enjoyable than a 'proper' sailboat in a more challenging environment (by which I mean weather, sea state, temperature etc).
On balance I think that anyone who is reasonably agile/fit/self-reliant who wants cheap, engaging, (did I mention CHEAP !?), accessible, independent day sailing/land-based overnighting and is content with and has access to a coastal/lake/river/estuary environment with good climate could do a whole lot worse than a sailing kayak as a first sailboat (and I would count Hobies as among the very best off the shelf packages available) either as a first step to 'greater' things or as a long-term proposition in its own right.