I read that sentence and it hit me right in the face as a strange, strange expression where 'tack' doesn't fit in as a noun, verb, or anything else. I suspect you meant "tact?"

Dismissing the criticism about rapidly changing CEO's is best done by pointing out case history, not with excuses and dismissives about out how unfair it is to do so because "they're just a start-up" or "you're criticizing for the sake of criticizing." It doesn't convince anybody to make those points.

Whether you intended it or not, you do bring up a fair point--Nokia itself was definitely not served well by holding onto a miserable choice for a new CEO for far too long. Going back to my examples, holding onto Balmer through the worst of Microsoft's years hasn't worked out well, nor did HP holding onto Carly Fiorina, nor did RIM during its time of holding on to two simultaneous CEO's.