Your Powerplay build might be great for running away,
Running away but
also killing ships which can't run away is the point. It's not just a binary "PvP murderboat versus everything else" - there are a substantial number of builds which can't tell the difference between my ship and one with all the internals stuffed with extra defences. So I can fly that and be assured that my worst possible PvP outcome is a draw (I escape, they don't get a kill) with a chance of a win, while still being capable of doing pretty much every PvE activity except mining and AX.
but it’s not a counter-argument to the fact that Elite Dangerous combat is fundamentally borked.
It's fundamentally broken
for PvP because it's trying to do three incompatible things.
1) Have NPCs and Players using the same ships and outfitting [1]
2) Have Players able to beat NPCs in many-on-one situations without needing to be an absolute combat ace
3) Have PvP exist outside of arranged duels where relatively comparable specs can be assured
You can't do all three of those at once. The second requires that a player-built combat ship (or even a reasonably combat-focused multirole) has substantial firepower and defence advantages over an NPC, which the first then requires is a spread of capabilities which can also occur between player builds. The third requires that it doesn't. Since PvE combat is
massively more commonplace than PvP combat, changes to the combat model to accommodate slightly more interesting PvP aren't going to happen.
And for PvE, the combat model is generally fine: players can generally win a lot of fights even in an underpowered ship, generally escape the ones they can't win, and with a better ship or more skill players can take on sufficient odds to feel somewhat heroic (CZs, megaship scenarios, AX, etc.). That's what the combat and outfitting model needs to do in >>99% of combat encounters.
[1] The original Elite didn't do this - your Cobra III was, even before any upgrades,
massively more resilient than any NPC ship. With a full set of upgrades it was basically the equivalent of a modern G5 build but the NPCs still fly C-rated ships. This was compensated for by 6-vs-1 being a perfectly normal matchup, so being able to easily win 1-vs-1 duels wasn't all that relevant. (ED does need to set up more many-vs-1 combat encounters because they're a lot more interesting: rather than dropping an Anaconda on you as a mission enemy, drop four Vipers at once instead.)