We don't talk about Pun-Pun
I...don't know about that. I mean, I like the "Slayer of Beasts" role of the Ranger, but saying that no one else can do it? Dr. Rudolph van Richten has faced many monsters in his day, and he was a Rogue (well, Thief in the original setting).look at the Ranger lore in 5e.
The ranger is a deadly hunter. The druid won't delve into arcane magics to do elementalism and divination to track and slay foes. The fighter won't tailer their combat gear for stealth, survival, and detection. The rogue won't hone their combat talents to stand up and survive a battle.
There's no reason a Dex-based Fighter can't be stealthy with the right background. And Druids have plenty of divination and elemental powers already, and they despise aberrations.