I'm not quite sure.
The OP didn't know what the problem was and wanted to know. Despite then admitting the kitchen was marmite which baffles me. If you know your kitchen is marmite then you know it has a much more limited pool of potential buyers. That's being in denial rather than not knowing what the problem is.
There is a resounding issue with the awful kitchen no one liked at all and the terrible layout where you have to walk ALLLLL the way up and ALLLLL the way down to a) use the kitchen, b) get into the lounge because of the total lack of thought by the person who made those design choices.
Most people totally understood this wasn't a choice by the OP to do those things; they were inherited by the owner. And they can't really be changed.
Ultimately if you have so many posters telling you this, there's your problem. It's nothing personal. It's not being vile. It's just something that a lot of people just aren't prepared to live with. They CAN see past decoration and taste differences, and that's part of the problem.
And you are still stuck with an awful layout that is either going to cost a lot to put right or you are going to have to live with.
So the OP needs to understand that they either have to keep their house on the market for ages, fully understanding that very few people will choose to even look at the house OR they understand the problems with layout need to be taken seriously with the price. Just because the estate agents have given a standard price based on square footage doesn't mean they are right about the price. Clearly they are not accounting for so many people disliking the layout and the kitchen but it's a very big problem with trying to sell.
As I say, previous posters have nailed the problem when they say it's essentially a house which needs a lot of work in the eyes of many, but has the premium price tage of a renovated house, that doesn't need any work.
Thing is, the OP liked the house. So it's getting your head around what appealed to the OP. I'm fairly sure that being £100k cheaper was one of those factors. The higher price alone, in an era where wages are fairly stagnant, acts to restrict the number of possible buyers because there's less people who can borrow that much money.