Yes & No.
If you are short on cash for hiring a SEO and your website is 15-20 pages, you can simply choose Wordpress as a platform, use Yoast SEO plugin and do all the basic SEO by yourself.
Now, if you are doing a website redesign for a fairly large website that has many moving parts, you might want to involve an SEO at the outset. Your SEO team will help you migrate the website to the new URL by mitigating loss of link juice from backlinking. They will also take care of the URL structure and architecture of your website.