It's not about ability. It's about integrity.
I've heard solo performances from all the Eagles, barring Meisner. Each performed a track or tracks that originally we're performed by a full band. They all provided their own accompaniment with just a guitar or piano. It's the most natural thing for a musician to do. Playing and/or singing along with a backing track is karaoke isn't it.
Felder maybe a fabulous guitarist, gifted song writer, excellent band leader and a decent singer but he's definitely bottom of the Eagles list when it comes to integrity.