It takes a while to do anything, so while you may make it harder for elected leaders to do bad things but you also make it harder for elected leaders to do good things.
The smart power hungry sociopaths will just create or move to positions of power where the term limits (and elections) do not apply to them and continue influencing the incompetent figureheads and ruling over voters. Becomes less democratic that way too.
Which seems similar to what is happening now, only more so.
People deciding who they want as leaders is democratic. Term limits restricting their choice is not democratic.
The real solution is the smart people taking the time to educate the stupid and ignorant ones rather then going "Oh Noes, the voters are too stupid, we should remove choice from them - even the choice of re-electing someone they want for another term".
It seems to me that 98% of the US voters who bothered to vote prefer either R or D, instead of the other alternatives. If you think they shouldn't then you shouldn't be trying to stop them against their will. You should be trying to convince them.
Unless of course there are no better alternatives. In which case, Democracy is working as well as it can, and your real problem is elsewhere.