I never said otherwise? I'm aware that Johnny has largely "wasted" himself in the years after the Smiths split, if you want to look at it like that - as I explained in my earlier post on his Madchester tinkerings. I don't see how the notion of him making music for enjoyment is weak, though - if he's essentially jamming with his mates, it's not going to be ground-breaking, is it? When The Smiths started, Morrissey and Marr had a shared vision and they wanted to be successful. Every note, every word, had to count. When The Smiths were over (as I've already said) Johnny had nothing left to prove, and still doesn't. He's made his mark, he's made his money, he could have retired to a Cheshire mansion in 1990 and the music world would have been none the worse for it.
Another point that I think is very important is that Morrissey and Marr inspired greatness in each other. There were occasional flies in the ointment - "The Draize Train", as you mentioned, and the absolute hash that Morrissey made of the beautiful music for "Some Girls.." - but generally they pushed and pulled each other to further ambition and creativity. This has lacked almost entirely in Johnny's solo work - he has never worked with a "Morrissey-like" figure (perhaps by choice!) with the same lyrical talent and aesthetic principles. He went instead for the lazy potheads and the sub-par indie bands of the 'new' generation, who don't inspire anything in him, and consequently his music becomes as lazy as their words. Meanwhile, Morrissey didn't immediately run for a Marr-substitute, but he certainly wanted music and writing of a similar calibre. He aimed higher than Marr in his post-Smiths efforts, and raised his own game to match.
Re: vocal melodies. I could listen to almost any Smiths song as an instrumental, purely for pleasure. "Bigmouth Strikes Again", "Boy with the Thorn", and pretty much all the first album - they are beautiful pieces of music. I would never do that with any song from Morrissey's solo output - the music simply isn't good enough. If anything, Moz' lyrics have carried his solo career when for other artists, it would have been dead and gone.