MechQuest (Artix Entertainment) blended turn-based mech combat, deep customization, and a whimsical web-based RPG vibe. No game replicates it exactly, but these capture its core DNA across several genres.
Consider what you miss most: single-player vs. multiplayer, browser vs. download, budget, art style. Into the Breach and BattleTech are the closest tactical heirs; Monster Hunter and Path of Exile scratch the customization/progression itch.