You can't force trades. If something comes up, great. Just because Rondo is an all star caliber player doesn't mean that he puts us anywhere close to contending.
We used a particular strategy in 2007 - get guys past their primes who were on bad teams that wanted to reboot. Minny and Seattle were ready to start the youth movement and that didn't include 2 ringless and aging hall of famers. Getting players of that quality is not something that is always available.
If you instead go for a younger player, they cost a lot more in a trade. If you get the older guy but can't make the other moves to complete the team, then you spent your future on a mediocre short term boost.
I would also point out that 2014 Rondo is not as good as 2007 Pierce. In other words, we don't have a player of Pierce's caliber (circa 2007) on our team. Rondo, our best player right now, was already on our team in 2007, adding to the talent level. If we want to compare this team to the 2006 team in hopes of trading to become competitive, we are already starting out in a bad spot without anyone of Pierce's caliber and we will need one of our other pieces on the team to reach all star caliber (Sully?) as Rondo did (presuming that Rondo is now in the Pierce role, despite not being as good).