Keep boiling down to the essential. The flowery and subtle have no place on a slide. Slides support a presenter. They do not replace a presenter. The slides are just the facts.
Most presentation programs are full of special effects.
They are sold by showing all the cool effects provided. Unfortunately, most first time builders try to use every effect available. Words and pictures come flying in from all directions. Slides shake, shimmy and spin in and out. Any movement is accompanied by other-worldly sounds or stirring sounds of great symphonies.