Wilted Flower SyndromeAs I lived through my 30's and into my 40's, I came to an observation: people are like garden plants: some spring up fast, others are slower to act, eventually they flower and then... some will just wilt while others cycle into a new flush.
When the garden gets overgrown, it is time to prune. Not to get rid of everything mind you, just plow under the stuff that isn't growing any longer, and give some other relationships a chance to grow.
Even if the marital contract has not already been voided in spirit or letter, marriage never justifies social and physical isolation. But a multi-year unwillingness to grow is certainly cause to dig up a plot and compost the garbage that isn't helping.
If the old wilted flower seems to have some life left, prune it back aggressively -- disengage from the unrealistic expectation that your partner is a satisfier of your needs, be non-confrontational but above-board about it, and eliminate soul-deadening habitual activities like TV watching alone, especially if you find it draining in any way -- AND put your effort into cultivating other healthy and emotionally rewarding friendships.
If the wilted spouse wants to flourish again, it will with or without you, but even if not you won't have wasted your time doting over the empty husk.