Espeon is not under-rated, just merely under-stated.
Espeon has been cursed since the original G/S/C to be less cooler than the all-black ex-OU Class Staller, Umbreon.
Despite having excellent Special Attack and Speed, the reasons it is overlooked is because:
- Basic Movepool, with standard moves. (A curse most Eeveelutions carry, really.)
- Frail Defenses, making it impossible to use for extended periods of time. Basically to be used as a Glass Cannon.
- Received a boost in the form of Magic Bounce, but now got outclassed by other common users.
[Credits to Fizz :3 ]
- Outclassed by the newer additions to the Meta-game.
[Credits to Fizz :3 ]
- Looks weird: Probably the most arbitrary reason, but a lot of first-timers prefer others, say, Umbreon because of its rings. A pink cat with a split tail and a red gem on its fore-head is not generally a top choice for favourite designs. A general preconception of not wanting to use a weird looking Pokemon generally evolves into full blown apathy.
A Dual-Screen Espeon was mentioned in the comments, but Espeon rarely gets to set up properly. It is a viable option, that can be well-exploited by experienced battlers.