That sounds backwards to me. Frontier is very much the "greatest hits" show, what with borrowing characters, plotlines and imagery wholesale from SDF, 7 and Zero— I can almost excuse it because it's a fun watch, but it offers very little of its own ideas (at least in the TV series). Delta isn't anywhere near that level; sure, it borrows some elements from Frontier, but only from Frontier, and they're mussed with to a much greater degree than any of Frontier's own lifts. But more importantly, Delta brings several new things to the table— taking place in a settled solar system instead of a colony ship, or having antagonists who are introduced with clear grievances and motivations, or the weaponization of music (OK, this might be lifted from II)— that clearly establish it as its own thing with its own personality. It's a messy show, and I don't think it comes together in an entirely satisfying way, but Delta felt to me like there was still life in the franchise yet.