The answer is maybe, it will depend on how competitive the sector of your business is. For example, if you have a business in a fairly common sector with many other companies in your area, you will likely need SEO and social media to propel you to page 1.
If your business website is one of a few in your sector and area, maybe you will not need to do a lot of marketing at all.
Having a semantically correct, high-quality website is the perfect foundation to build on. Once this is complete, things can then expand on to SEO and social media marketing if required, which will provide brand awareness and search engine visibility.
Using a website builder without the knowledge of websites, or a very low-quality website designer to build a substandard website is a recipe to fail online, unfortunately.