^^^ Ford was pushing 40 when he did Raiders; in his forties a few years later for Temple of Doom; nearly 50 for Last Crusade, and well into his 60s for Crystal Skull. Fillion's only seven months older than I am; at 42, he's still plenty young enough to pull off the role.
Not that I'm behind that. I don't think the series should be rebooted. I think it should be left alone, like all classic films/series. Besides, nobody can play Indie like Ford.