What's wrong with was? Nothing, unless there's something that could be used in its place. Something that will bring the sentence to life -- give it some spark -- add some pizazz.
Verbs are a fantastic tool for writers ... they can describe the action; intensify the emotions or dialogue. But you have to make sure you break things up a bit. I'm using the 'was' example, because it's one most of us tend to fall back on -- and one that I've had many editors and critique partners fling back at me with comments such as: "You're using this too much -- can you find another way to say this?" **Okay, after about the tenth time their comments are bit less diplomatic, but you get the drift. ;)**
There comes a point when we have to break out the Thesaurus and start looking for different ways to say the same thing. I'm one of those people who tends to get a little irritated with word repetition. I don't often catch it in my own work until that final edit, but let me tell you it is really a big pet peeve of mine. Just ask any of my critique partners. On second thought, don't ask them.
Yet sometimes, no matter what you do, it isn't easy to 'say it differently'. For instance, do you know how many synonyms there are for the word 'door'? Not many... and even fewer you can just slide easily into a sentence without sounding like you're using a "Word of the Day" calendar to write. (Been there, done that...have the bald spot to prove it. ;) )
So, what do we do with was? Like salt or pepper ... use it sparingly or it can overpower your prose. The same goes for adverbs. Sprinkle, sprinkle, sprinkle! No dumping allowed! ;)
If you can think of a better way to 'show' the reader what the character is doing or feeling, then use it! It might mean re-writing an entire sentence or paragraph, but that's all part and parcel of this gig. If you can get in the habit of 'showing it better' from the outset, you are way ahead of the game. Otherwise, save it for that round of editing to come. Just keep writing, no matter what. As the great Nora Roberts is fondly paraphrased: You can't fix a blank page.
By the way, don't completely cut any word from your writing. All words were created for us to use, and 'was' is no exception. Like any other part of the writing craft, it takes trial and error to find your voice -- including the words you use.