The phrase "limited effectiveness" means that something does not work very well or is not very successful in achieving its intended purpose or desired outcome. Full definition
While some types of assessments were effective (such as providing feedback), others had limited effectiveness in classrooms. (edutopia.org)
Unfortunately, better communication from scientists will have only limited effectiveness as long as the press continues to drop the ball. (realclimate.org)
These games typically receive very few bets which limits the effectiveness of betting against the public. (sportsinsights.com)