Why can't you find words? In most cases because you don't know Hebrew well enough. But this is exactly the point (and the catch). You use your dictionary because you don't know Hebrew well enough! What exactly is the problem? Although your frustration is valid, your dictionary is very likely to have the word that you can't find, but it is not "smart enough" to understand what you want. Why are most of the existing dictionaries not "smart enough"? Because manmade instruments are only as "smart" as their designers, and the designers of most of the Hebrew dictionaries don't think of you, the English speaking person. Rather, all the dictionaries are made to serve Hebrew speakers who want to learn English. Why is that a problem if these dictionaries still have both Heb/Eng Eng/Heb search functions? Since the designers assume that you know Hebrew, their emphasis is on input of Hebrew words into the dictionary. This is your weak area. You don't know how to input the words into your dictionary.
What's wrong in the way you input words into the dictionary?
Since you don't know Hebrew well enough, you input your words exactly as you see them: you are trying to read some Hebrew text, you come across a verb that you don't know, you type the verb exactly as you see it in your text -- your dictionary does not find it!
It does not find it since the word is very likely to be a verb in a conjugated form thatthe dictionary does not understand.