They've tried that approach (generic forms) many times and it's always dreadful, won't be any different this time. Players want to actually transform into specific beast. Generic forms are balanced, practical, but don't scratch that itch.
Yes, I know it means extra pages of stat-blocks appended to your character sheet. Thems the breaks.
Hardcore DMs require druids to meet the animals in nature first before Druids can wildshape (or Polymorph) into them. This serves two purposes, 1) keep beasts mysterious before discovery, and 2) make finding new beasts part of the exploration game.
