Quite frankly, the first biggest problem bards have is that they're tied to the lute playing nancy who prances around and goes "fa-la-la!."
This is what people think of when they think bards.
In other words, bards are looked down on because
lutes are lame. It's an image problem. Have you seen most of the pictures in the 2e Complete Book of Bards? It's the sissiest thing imaginable! I blame the problem on this bizarre need people had to force D&D to be a psuedo-medieval game in as many annoying ways as possible (This is the source of a
lot of issues, in fact), while ignoring that the game is about dungeon crawling. The fa-la-la dandies might fit in a cheesy "oh god this isn't at all how it works" medieval tavern, but they don't fit at all in a dungeon or any combat situation.
It's a similar problem of monks, I think. Monks were divorced from what could've been cool wuxia style characters, masters of martial arts and swordplay, torn between believing in a full sanctity of all life and the need for justice...and turned into really terrible 70's kung fu types. Bards went from powerful druidic sages, a jack of all trades and master of
many, to "fa-la-la, isn't today glorious my adventurous friends! Come, let us prance about the maypole in a gay old fashion!" Look at how cool you can easily make bards when you get rid of that garbage:
The half-orc bard that slams on his drums as the battle rages on, introducing a primal beat to every step and attack? Awesome. The dwarf bard that speaks in poem of the glories of his ancestors and their deeds as he kneecaps the enemy? Awesome. A large and ornately dressed man who sings his arms wide and sings, causing the mountains to crumble and the world to reshape itself to his command? Awesome. The mysterious woman followed by the spirits of the dead who do her bidding as she plays her flute? Awesome. The Dark Sun bard who doesn't play an instrument, but instead uses his charm and charisma to allow him to operate as an assassin? Totally awesome!
The poncy guy in green who plays a lute and sings "Fa-la la!" as he goes along?
As un-awesome as you can ever humanly be. Consequently:
almost all the images you first get when you look up bards.
I'm in a 3.5 game right now where I'm a caster-bard (going Sublime Chord) who plays a fiddle. Our BBEG is a lich bard who plays a guitar. Just pause for a moment and grasp how
awesome that final battle is going to be.