Power Play could have been (and still could be) amazing, but it was the moment it was added because the gameplay and end-goal wasn't compelling or sustainable. And perhaps mostly because PP was and is a seperate, aloof, and abstract layer that is divorced from the main game. This resulted in a simplistic 2 mission grind mechanic that feels artificially overlayed like a layer of rigid slime.
It's almost like they wanted to add a new game mode that had minimal impact on the main game, while still coexisting with it. What did they think would happen? It's basically a PVE version of CQC. A graveyard because it's almost irrelevant to the main game.
I probably won't get much agreement here, because everyone on this thread is burnt out on Power Play as it currently exists. Your assessment of PP is fairly accurate, but I'd argue that FDev never intended it to be as monotonous as it currently is, or rather, FDev never intended it to have as much player participation as it did for the first year.
Remember the Beta mechanics? Internal competition for Power Ratings, with CG-like percentage based rewards for varying levels of contribution; No salary; and FDev/GalNet authored stories depicting the political influence and machinations occurring in Power Play.
That original concept was the definition of 'end-game' and 'team PvP'. Sure, actual PvP wouldn't reward you, but you got to wave a flag and blow up other ships with opposing flags. And because only those rich, loyal, or with time on their hands would participate, you'd know every pledged CMDR in Open was fair game. That is something I wish we got to play for a couple months before they took it back to the drawing board. There simply would not be any grinders, because all the weapons would be both difficult to get, and mostly useless. So you'd wind up with saboteurs and loyalists in every Power, guiding as they saw fit, and there would not likely be any Power with 'unstoppable' expansions. That could have been fun, even with current (limited) mechanics.
After FDev caved to the beta feedback demands for salary and reducing internal competition, nearly all of the mechanics had to change over the next 5 months to make it functional. Hell, 18 months in, we're still at the point where the basic mechanics have to change for PP not to be a frustrating and highly exploitative mess.
I'm not saying FDev's Beta version of Power Play was the best meta-game ever, but it would have remained limited and running in the background for most CMDRs. It wouldn't have drowned out the entire human bubble in coloured political alliances.
As for sustainability and dynamism? If you still had to pay funds to fast-track fortification, and you did not get any reward for fortifying, would
anyone have ever fortified a system further than 60Ly away from HQ? Maybe, but clearly not to the repeated amount or the prep numbers we've seen over the past year.
Power Play didn't fail because it wasn't thought out, it is failing because they've hot-patched a meta-layer built for 1% of the gaming community so it's appealing to 90% of it, and then had to back-track to patch easily exploitable and abusive mechanics when you take in that other 89% of players.