I don't agree with that at all, I think Mirko's success in MMA was partly because he wasn't your standard kickboxer depending a lot on combos and misdirection, he was always about focusing on powerful counters, the LHK, the left straight, the mid kick and even his lowkicks were often picked out one at a time and he went further in this direction in MMA.
The problem was his style was very dependant on speed/reflexs and as those declined he couldn't pick out his big counters anymore nore defend himself as well. Latter day Crocop returning to "K-1" actually reinvented himself as a very different fighter focusing more on a tight defence(allowed by the big gloves) and strong clinch work and close in boxing.