I think there's a lot of value in having these ex-pros on, even if they mostly come across as useless. If they were used in a very narrowly defined punditry role - to talk about the playing side of the games - I think they're great. There's not many people out there I'd rather listen to talk about how a centre forward should have positioned himself, for example, than Alan Shearer.
The problem is that there's more to talk about when reflecting upon a game than just the playing aspect so they should get experts in those fields on the panel too.
Ideally there'd be a 3 man panel;
- a player to talk about playing stuff (positioning, what it's like in the build up to a game, how a player should have done X, Y or Z, etc);
- a ref to talk about the laws of the game (as interpretation of this does tend to be an issue in most games)
- a manager to talk about the overall approach each team has taken.
The way it tends to work is that most of the punditry slots are taken by ex players (with a few small exceptions with people like Souness who also managed). So we end up with people like Shearer being the guy who gets to spout off about something he's not an expert in (e.g. the laws of the game) so ends up being all over the place.
Not sure why more retired managers & refs don't take these roles. Maybe they're not offered (more demand by Joe Public to see someone familar like Jamie Redknapp or Henry rather than Houllier, etc).