No Ed, these skills are not mutually exclusive and I can point you to a bunch of folks who excel at both.... drop in to the Cakewalk Songs Forum and have a listen to some of the music written and recorded there.
I'll make sure to watch the next Grammy show and look for "best writer on the Cakewalk Songs Forum".
I am talking about being George Martin, Mutt Lange, Brian Wilson, Rick Rubin, Quincy Jones, Tom Dowd, Jim Steinman, Steve Popovich, Phil Spector, Roy Thomas Baker, Jerry Wexler, Jimmy Iovine..... the REAL industry heavyweights. I don't know who is in that forum, and I won't be visiting to find out, but being the best writer and producer in your own home studio isn't what wins awards or gets you into the rock hall of fame. Remember, the best guy YOU know is likely not even on the radar of the real music business.
This is all about perspective. I never had the opportunity to live "the dream". I wanted to tour on the bus, play every 3rd day in another city, sell the arenas out, watch t-shirts sell faster than they could be produced, win the Grammy, have gold records on my wall. I am just not good enough. I lived the delusion that I was good enough but didn't have connections and that's all that was missing. It took until my 40s before I accepted the painful reality that the problem was my limited skill set. The best bands to come through my area were The Raspberries and The James Gang. They both contained members (Eric Carmen and Joe Walsh, respectively) who went on to bigger things, but their success as bands was limited in the biggest scope of things, yet still FAR beyond anything I ever did. I was in some really good bands, but good is a relative term. In that same bigger scope, no we weren't really all that good.
Honesty, while sometimes a bitter pill, is never a bad thing. Think about how many AWFUL singers you know that continue to attend every karaoke night and be laughed at because their "friends" continue to tell them they can sing. Is it fair of those "friends" to not be honest? Those same people wind up as the comic relief on American Idol.
When I look to the ultimate hybrid artist, I think of Todd Rundgren, who also belongs on that list of top producers (Bat Out Of Hell, anyone?). He writes it, he plays it, he sings it, he produces it, he engineers it, and he does much of it on software he wrote himself. However, he is a rare breed, and people have actually heard of him.
Without the Cakewalk Songs Forum.
Remember, perspective. What do YOU consider a success? That will color your input on discussions like this.