your theory is actually quite easy to disprove. teams don't get good by consistently drafting in the lottery. much to the contrary, teams get good by getting 3-4 picks right, then surrounding that talent with role players who know their job.
OKC didn't stay in the lotto forever to stockpile talent. they drafted well in their three opportunities in the top 5 (KD, westbrook, harden) and then they went to work building around those three while the team gradually learned how to win in the regular season, the first round, the second round, etc.