I think the issue is that techy/engineer-types are big fans of elegance. It's undeniable that services like Zapier are elegant in the sense that they generalize pretty well, they can "do it all" and, in all honesty, they're not too hard to figure out. With that said, there's no true value in elegance. And while generalizing is definitely a good idea for a mathematical proof, it might be a bad idea for a product.

I have to admit that a lot of times (especially when building side-projects/toy startups), I second guess myself when it comes to these kinds of product decisions -- "Is this product too simple? Too bare-bones; too much of a one-trick-pony? Would anyone pay for this?"