Well there are a couple of different issues here. I had to have a few painful talks with my DH when we were young Parents , because he needed to make love, more than I felt like it. His experiences were after all different from mine, as I had physically had the children. I was a SAHM so wasn't overly stimulated during the day.
My life had changed a great deal more than his, after all.
I said to him that I was more than willing to satisfy his needs but that there would be occasions when I would just like him to get on with it. Personally I knew I could make love without being very involved. ( just lie there mode)
He felt guilty because he wanted me to WANT to make love to him as much as the other way around. He didn't feel happy with 'using me' as he saw it. He is the most decent person in the world.
However, I wanted him to be happy, I couldn't at the time do what he asked, and so he just had to get on with it.
But when he got going, more often than not, I got going as well.
I wanted to keep the physical side of our life going as i felt it was very important. I knew that I wouldn't always be tired and it also helped us feel closer together.
So to answer your question do things improve? Yes they do, as your DCs get older and less demanding. You then have more time for you and your DH.
Try and factor some 'You and him' time in there. I got a massage book and some sex toys which helped. At least they make you laugh. Laughing together makes you relaxed. Nice hot bubble bath together, wine, evocative music you like, etc etc. Embarrassing as it may be, you need to talk about sex with him.
Above all, try to look for solutions, not blame, as resentment is a passion killer.
Best of luck as it is not easy. Relationships, I mean.
Try a Mindfulness course for help with relaxation.