Powerpoint is an excellent tool - I use it a LOT!
The problem is in meatspace.
I am frequently subjected to numbers of appalling Powerpoint presentations - the biggest culprits are:-
Trying to be clever
Bizarre (or boring) backgrounds
Weird and/or illegible fonts in profusion
Stuff zooming in and out with sound effects
Individual slides so busy that they look like a greeked palimpsest
Incomprehensible (and illegible) tables
Ditto graphs
Text indistinguishable from background
Ridiculous "WordArt"
and so on....
My rules:-
Plain background (I usually use black)
Only one font (I like Roman antique)
Only two font colours (I tend to use white and orange)
Only 3 font sizes (from 44 to 28 points)
No "active" slides (God, I hate them!)
Small, nondistracting "decorations" for each slide for interest
Very little on each side, but LOTS of slides
> 10sec for each slide
Lots of pictures (only one or two on each slide)
No arrows/pointers (shouldn't be needed)
Judicious humour
Careful balancing of elements
A good presentation should balance information with a degree of entertainment
It takes a lot of time to do and is quite an art.
