Your website won’t really be custom.
Website builders come with a limited number of themes, templates, and layouts. This can lead to most website builder sites looking very similar to one another. If you want convention, use a website builder. If you want customization, you’ll probably need a website designer.
Steep learning curves.
Some website builders, particularly the cheap ones, have a steep learning curve. If you are a coding newbie, you might need to do a lot of research to figure out how to use it.
Without a designer or photographer to help you, the site may end up looking a bit hodgepodge. Drag and drop interfaces mean you can put elements where you want them, but your website may lack design unity.
There is often a lack of transparency about all the associated costs (hosting, domain, website builder, ecommerce features, email, and any extra integrations). Additionally, if you terminate your website builder contract, you will lose the website.
No SEO optimization.
You’re on your own to write good content, which means that nobody will tell you how to do good SEO.