A poorly constructe website will affect crawling as well as seo rankings. one must remember that important pages should be accessible in 2 or 3 clicks from the homepage, content must be categorized according to topics, a breadcrumb path should be established, and good internal links must be created.
Content does not have to be wordy to receive top rankings for its sites search engine results page. short articles that provide comprehensive coverage of the information sought by the seeker win against long-winded writing.
Bad internal linking is the one that causes the most problems in my opinion.
poor planning right from the start will definitely creatte problems later on, particularly if additional pages are going to be created without having any specific position on the website. imo i would first of all identify the main subjects nd then ensure that all pages of relevance have a proper connection starting from the homepage.
I keep the site structure simple. Put related pages in the same category and link them together where it makes sense. Visitors should be able to find what they need easily.