There is no single, isolated alternative to tanking, just as tanking is not an isolated solution to losing.
There are just a shitload of other things that can happen in different combinations that make tanking unnecessary.
The two key things are:
1.) Changes in chemistry.
We have no idea what the relationships between players are, and how that affects the play we see on the court. Basketball is an extremely team-oriented game, and players have to be on the same page. The acquisition or departure of one single body can change everything. A shift in the mentality of one single body can change everything. Everything. And this includes the coaching staff, and anybody influencing the athletes.
2.) Internal development.
Never forget that this is just a whole bunch of people doing something. People are fickle. Remember when Salmons was a revelation on Milwaukee? I do. Wasn't though, was he? Remember when MCW looked like he had never seen a basketball before in summer league? Remember when the absence of Kendrick Perkins was the reason Boston lost to LA in the finals?
Remember when Vince Carter was just a freak athlete who didn't age well (some people still believe this)? Remember when Stephen Curry was too small? Remember how hopeless Boston and Phoenix were this year?
Nobody should be dead-set on tanking.
Too many variables.
You make up your mind on anything, ever, and stop taking in new information, you're a sucker.