Giving the reader what they want isn't always easy and it sometimes it just isn't possible. You aren't always going to be able to please everyone and to try can often be more detrimental to the story than anything else. I don't think you should write to only please the reader. I believe the story comes first, always, what I'm talking about is hitting the points of expectations by the reader.
If you say your book is a thriller than it should be fast-paced, full of action and not pages of thoughts, rambling dialogue and end with a whimper. I will say I don't get the Dark Romance that is popular right now, I haven't read it at all because it doesn't appeal but one thing I've noticed is that the reviews are so mixed because the expectation of what the reader was getting wasn't clearly set. These are bad reviews that could have been avoided, no one wants bad reviews but when they could have been avoided that just seems like the biggest loss of all.
One of the pluses of the indie storytelling is that the previous point by point elements to a story that were required for a publisher to give a green light aren't there anymore. One of the best stories I had read in a while is an example. I read an interview where the author had to go back and add a love interest when he was done. It was an extremely good book and the love interest, really didn't add to the story or the character. For the most part, when I'm reading a thriller or mystery, I don't find a romantic element is always necessary but maybe that's just me.
I highly recommend that after you've hit the end and before you go back into revise and edit, hit up Amazon and Goodreads and find books that are as close to what you wrote and read their reviews and find out what most please and most annoyed the readers. You can't walk up to someone ask them what they like the best and what they are looking for in a story but with reading reviews you can see it all laid out. Does your book fall into a trap that readers feel is tired and there is a way to fix in revision? Is there an element missing that readers love and could add value to your story?
There are minuses to not having a publisher green light, how do you know you are giving the reader what they want when they hit buy? I believe reading reviews will help you know that, it takes time, it can be long and tedious and a little boring but so is editing and it's the most important part of writing your story.