That also doesn't answer the question of what you posit as a plan, or seeing worth in somethign different than your vision. I don't even know what you think. you dismiss any progress made, and you dismiss lottery (maybe? can't tell). So, what is your idea of a plan.
I don't believe the Celts are certain to be mired in mediocrity. In fact, I believe in Danny Ainge to find a way to the promised land again.
I just can't figure out a plausible path to get there right now. It's too murky. I spend so much time wracking my brain trying to figure out how the Celtics are going to become exciting and genuinely competitive again, and I just don't know. There's too much uncertainty. That's frustrating.
The name of the game is "flexibility". Don't commit to middling players like the Pistons did when they signed Ben Gordon and Charlie V, or the Pelicans did just because they desperately wanted to surround Davis with some talent.
Of course, it's a lot simpler to flat out tank year after year and hope the ping pong balls fall in your favor, but that's just as uncertain as any other rebuilding "plan". It only looks like a plan because it allows fans to convince themselves that "this is finally our year".
If we agree that an NBA team needs superstars to win a title, we also have to acknowledge that they're incredibly rare. We can't simply go out there and get one, we have to wait until one becomes available. Then we have to convince said superstar to play for us, and we either need desirable, matching pieces if we want to trade for him, or a successful/promising program if we want to sign him in FA.
Say what you want about the sixers' "plan", but they're not going to convince any superstar to sign for them in the near future. Neither did the whole tanking thing help them acquire one, yet.
They are rebuilding, we are rebuilding, and neither team is closer to winning a title than the other. The difference is, we have playoff basketball, we have success stories, we build actual values in the form of increased reputation for our whole program, all with a core of rather young and cheap players.
So, you can either focus on the negatives, that we're far away from contending, or focus on the positives, that we're just as far away from contending as any other rebuilding team without a superstar, only with more intermediate success.