I think there's always been this conflict with Morrissey between longing for someone, but also enjoying his own space and freedom.
I think he's always romanticised the idea of finding someone who loves him and that he loves in return. But the mundane, day to day stuff like sharing a house and going to the supermarket he probably finds quite boring and stifling.
I often think of the bit in The Importance of Being Morrissey where he says "I don't think human beings get on" and that he can't imagine how or why living with someone would even take place. Of course, we now know that Morrissey did in fact have relationships with Jake and Tina in the years prior to that documentary. Something which he didn't talk about in it, but later revealed in his autobiography.
If Morrissey had settled down into a wonderful, long lasting relationship with someone then it's difficult to see what he would have written songs about. I think what he does for a living is a form of therapy for him. If he had this happy and fulfilling personal life, then what is there left to say? The race is run, you've found your happy ever after.
I study lyrics by other artists about unrequited love and failed relationships, and then you Wikipedia the songwriter and you find out that they've been happily married to someone for 20 years. And I wonder, do they believe in the songs they write? Are they autobiographical? I can understand a perennially single person writing songs like that, but when you're married to someone I often wonder whether they demand to know if the songs are about them or an old flame? I can't imagine writing a song like "I Know It's Over", showing it to your wife and then kissing her goodnight. Wouldn't she have...questions?