I don't really know much about gravel bike, but is choosing a gravel bike more limiting or does it give you more options because they are equally good on the road? If it were my first bike when trying to get into it, I would definitely want it to be comfortable as a road bike. I'm assuming that local clubs are more likely to have road rides, but I also don't have a clue if that assumption is correct.
Regardless, I can't see why you would buy anything without pedal assist. Speaking from experience, it will allow you to ride more and longer, but it also will encourage you to do it more often. It looks like the Diverge is as much or more than Specialized ebike options. Just a lazy man's two cents, fwiw.