"Why are ghosts not used to lockdown BCs or carriers?"
"Why isn't bio/vessel used against Protoss?"
"Why isn't restoration used on vessels?"
"Why aren't valkyries used to kill interceptors?"
"Why aren't valkyries used to counter mutalisks?" (Commonly asked in the pre-2018 era!)
"Why isn't mech used against zerg?" (This was commonly asked before mech switch was popularized by Fantasy/Flash/others in 2008-2010!)
Sometimes, there are fundamental reasons why a unit or strategy is bad. Other times, people think they know why X is bad, only to be shown by Fantasy, Ssak, Flash, Bisu, Effort, ... that X isn't actually bad.
Let's discuss: what commonly-asked-about units/strategies are *actually fundamentally bad*, in that they will never ever enter the meta in the next 10 years? And what might be simply a matter of figuring out the right way to use a unit or approach?
Example: "Ghosts can't be used TvT against battlecruisers because tanks often supplement battlecruisers, and tanks have much longer range than lockdown."
"Corsairs aren't used against Terran beause Disruption web requires a fleet beacon, at which point carriers are a much better use of the money -- but it could have situaitonal use to stop sharp timing pushes, or supplement with carriers in cases where storm is infeasible (e.g. a vulture-heavy terran, or a semi-island map)."
(Fundamental reason, but allows for exceptional cases)
"Restoration isn't used on vessels since APM issues, and medic energy is low when plague is out -- so most medics won't have enough energy to restore vessels which must be active on the map at all times. There could be meta shifts with fast medic energy upgrade + more medics are produced, and terran 3rd gas earlier, that make restoration feasible"
(Nuanced reason, opens up possibilities for use conditional on other meta shifts).
I made these reasons up and they're maybe totally wrong, but the first reason is "fundamnetal" whereas the last reason is "in the current meta, there isn't room, but perhaps with changes XYZ it could be feasible."
Let's not forget how many threads were devoted to why Dark archon isn't good vZ (until Best v Action), how mech isn't good vZ (until Flash/Fantasy/others popularized), how Valks weren't good vZ except for very narrow valkonic pushes (until Remastered bug fix and recent meta shifts), ....
Often times, things aren't good until they are. But some things are fundamentally bad. I'd like this thread to open up a discussion between which is which.