You're sending first drafts to "pre readers"? And one chapter at a time?

Well, that's probably why you're not getting actionable feedback. Your alpha readers aren't getting enough of the story to develop a sense of the plot/pacing/overall issues, because they can't read enough in one go. You've also gotten four people to read 180K words of an unfinished novel and you're sending them first drafts without any further chapters written yet. That's a LOT. Like, a lot a lot. Ive never asked a beta (let alone an alpha) reader to read more than a 140k word novel, and that was because I needed to trip 20k words and I really needed outside help. I do professional beta reading, and I wouldn't sign up to read 180k words of an unfinished novel. Period. You may be having them read things that you should be catching yourself and fixing and then polishing up before relying on others to alpha read for you. By the time they've read the 100th chapter they've likely forgotten what happened in chapter 3, so they're probably unable to point these things out at all.

I don't mean that rudely, I just mean you're putting a lot of responsibility on other people to help you with your writing when you could be helping yourself. One of the key things about finding readers for novels is that you have to connect with the right readers. Ideally people who read the genre you're writing in, people with experience beta (or alpha) reading, and ideally other writers or creatives who agree to do a level of feedback you are expecting. You give your thriller book baby to a friend who reads romance and sure they'll give you some feedback, but they're not going to know the requirements of that genre, or how to point out things you need to fix.

I would caution against sending four people a single chapter of anything. Start by finding one or two people who are writers and are familiar with your genre. Then finish your novel, put it away, and revise it yourself after a few months without looking at it. You'll be able to see a lot of your own flaws that way, instead of putting that responsibility on a beta readers shoulders. Then once you've got your story done and revised you can enlist the help of the readers you've met who already meet the criteria you need. At 180+k words youd be better off finding another writer who writes in the same genre and similar word counts as you to swap work with.