Orm, what you describe wouldn't be good enough for me and it doesn't sound good enough for you either tbh
I thinks it's true that children change you and can wear you out emotionally, they definitely take something away from your couple relationship because everything is naturally focussed on them while they are growing up - we had a pretty crappy few years when DD was 13 - 16, she turned into a vile little thing and when DH worked away, then worked horrendous shifts, I couldn't always handle her, we had massive arguments and I suppose I resented DH for working away, working nights etc. he was sometimes glad to get away because I suffered from horrendous PMS at the time too .
We went through a pretty rough patch when we absolutely questioned our relationship but in the end, neither of us wanted to end 20 years of marriage without trying to work things out, which we did and we are stronger and happier than ever.
What you need is more couple time, have you got anyone to dump the kids on for a night or a weekend?
I used to wonder ( and be quite judgey) why my SIL farms her boys out to her PILs every weekend , now I think she's helping her marriage by having regular time alone with her DH.
I think you do need to make an effort with your marriage, both of you, it's no good when it's one sided - a cuddle in the morning before you get up, a phonecall during the day to say hello, a kiss when you come in at night, it's nothing huge, just lots of little acts that say you care about your partner - DH gets in the bath most nights and if I don't get in with him , I sit on the loo while he tells me about his day at work/asks about mine and I scrub his back or he fondles my boobs scrubs mine. .
It's basically about making time for one another and actually feeling heard and valued - contentment is great within a marriage, complacency, not so much.
I also think that by confronting things now and working together, you'll have a much more solid footing when the kids have grown up and flown the nest - DD now lives 40 miles away at Uni and has done for the last two years, we love it when she comes to visit, but we love having the house back to ourselves when she goes home.