This is a good point, and it's an interesting issue to chat about. All the parts of your book should be your best writing, but the first chapter - the one which will hook your reader - needs to the most be your best writing. And of that chapter, the first three sentences may well make or break whether the prospective reader in a bookshop takes your book to the checkout, or puts it back on the shelf and picks up someone else's book to buy. With the first paragraph, the reader is going in with a blank canvas, but you the writer already have a full oil painting in your head, vibrant and rich with colour. In order to hook the reader and ease them in, you have to do a great deal with very limited verbal real-estate to work with. Every word you choose must be judiciously chosen and ideally accomplish multiple things - for example helping build both the world and a sense of mystery at the same time. So yes, you're right, cutting for the sake of cutting is disastrous generally speaking. Cutting words should be done with the same care those words were chosen with in the first place. But saving words is different, it's simply being word-efficient and this is arguably the most important in your opening paragraphs. You can afford to be wordy for the joy of it mid-book when the reader is already invested. But to indulge in that at the start when there's work to be done introducing plot/characters/world/time/location and so on - things which the reader needs to quickly learn to avoid confusion - could risk turning potential readers off. Some examples of this being used in literature are when the opening words are carefully chosen to deliver interesting punch, which might compel the reader to continue. For instance Bilbo Baggins and his eleventy-first birthday, in the opening of Lord of the Rings. Or Winston Smith hearing the clocks striking thirteen in Nineteen Eighty-Four.
