Gotta walk before you run, right? Without the ability to save, adding in a quick restart function would go leagues for both testing and accessibility for the player. What better way to find bugs than to let someone quickly run right back into them while playing normally?
Were I to try to pin down the issue more directly, I'd say it's the lack of ability to prevent the full sequence from beginning. Being able to struggle rapidly out of the initial grab, rather than being dragged under and going through the full struggle, would really make things less aggravating when retreading old ground. That's a problem that a lot of games overlook. It's fine the first time, but what about the second? The third? Maybe even the 8th? Even really GOOD things get annoying at that point, especially if you're dying because of difficulty ramping up. The issue with the vore was the speed. I think the struggle system you made is really neat, given that it's normally just button spam. The issue it brings is in speed, as you can't just spam your way out once you're starting to get annoyed with the frequent stop-go of running into effectively invisible enemies.
In short: Consider adding a brief window to escape immediately before getting pulled into the "swallowed" state. Maybe allow a single QTE that makes the monster spit you out instantly. If you fail it or don't do it, then you get sucked down. Keeps it interactive, but speeds things up. Doesn't intrude upon getting vored, either.
That being said, the enemies do NOT suck. The game's very early on, and as you said, you're learning! Don't be that hard on yourself! Can they be improved? Definitely! Do they suck? Absolutely not. The enemies themselves are pretty neat! They merely need refinement to really shine as their own entities! And that comes with time and experience. Nobody starts at greatness, least of all perfection. Give yourself some more slack!
Hey, as a player of many games, I appreciate the addition of options! You'd be shocked (or perhaps not) by how many people making fetish games forget that their players are there for the content. What's the point of a niche game when the niche content is awful to experience because of bad mechanics? Having that included so early on is a grand sign.
I'll definitely give it a try soon, especially with such a rapid response to feedback! You're certainly on a great path of growth, so I wish you the best of luck with your development going forward!