I guess it depends on what kind of thing your focusing on. I’d consider a custom website to be an excellent place to show-case your skills if your skills are relevant to making a good looking website, like a web designer. Otherwise I wouldn’t care too much about what technology you make your website in, as long as your skills are up to expectations with the jobs your applying with.
For example, a back-end developer could have their website done on Wix (or something similar) and it wouldn’t matter since making “good looking websites” isn’t their area of expertise.
Regardless, its always good to have references of previous work, when job hunting. Just don’t build the website in Wix and say you built it from the ground up. Just don’t think its 100% required, unless your set of skills are oriented toward building front-end, “designed” web sites.