I think your intended use of the H9 is perfectly valid. Blending an effect from zero to any level is a great idea either in use or during preset creation. The effects should do that and, in fact, almost all of them do. I think the H9 can easily do this and that there IS one simple thing you have overlooked.
Many of the 52 algos have a mix knob at the top left. In most of the Modfactor algos, you should use the Depth control for this. Yes, it is natural to try the intensity control. Yes, the “Info” tab should explain this (it is good but imperfect). I suggest you try the Depth control. Some algos get “out there” and even the Depth control does not remove the effect. Undulator and ModFilter are two of them. But there really are very few of them.
I also think you are correct that few factory presets are subtle and it takes work to make them subtle. I have come to believe that the reason for this is that the H9 is a victim of its own success. It covers soooooooo much ground and sooooooooo many different types of musicians and composers use it that it is impossible to give everyone what they want in just 99 presets. Shoegazers, synth players, movie score composers, DJ’s us the H9 as much as rock and blues cover-band guitarists.
I’m in the latter group and I’ve created a couple of preset lists that may be more to your liking. In one, I try to make the H9 sound like popular vintage effects and name them as such so it is easy to understand what the presets do. I suspect trademark concerns limit Eventide’s ability to do this. The second list has more advanced use of the hotswitch and exp ped. If you are willing to post your email address here, I’ll send them to you. They are not perfect but you may find them easier to work with.