The thing that so many experts forget is that basketball isn't baseball, where one can simply trade an aging star for a bunch of cheap minor league prospects. If that could happen in basketball, Pierce and KG would probably have been traded long ago.
The fact that we have to take back equal salary really diminishes most of the value of trading PP or KG. To compound the problem, unlike say football or baseball where depth is very important, the NBA is a league of stars. Trading PP or KG for a couple role players really doesn't do much to help our rebuilding process.
To me, most of the trade scenarios being tossed around don't do enough to justify trading away two players of KG and PP's magnitude. It'd be like if you had to raise a million dollars (getting back to winning a title) and you had 500K already. Then someone offers you a deal that you don't feel good about and would give you a hit in the short term, but would eventually get you from that 500K to 525K. Sure, you eventually make a little money, but it gets you nowhere near your goal and you have to feel badly about it. Just doesn't seem worth it.
Now, it'd be one thing if someone was offering us the next cornerstone of the franchise for PP or KG. But that wasn't happening 2-3 years ago, and I can't imagine that is going to happen now.