While the title may seem click-bait-esque, I really am here to tell you why you shouldn't use WordPress for your website (unless you know what you're doing). I'm going to summarize it into a few main points, so let's dive in.
I myself have hand-coded themes, as well as made use of 3rd party themes (such as X or Pro). I've used Cornerstone, WP Bakery's builder, Oxygen's page builder, and even plain-old custom fields for content construction.. And there are a lot more ways to build a site out there, not even including all the plugins for various features (want a simple slider? Good luck picking one out if you've never used one before and don't want to hand-code it). My advise? Find a method that works for you and stick with it, but make sure that method has a history assuming you're not going the custom fields route.
I may be exaggerating a bit, but not by much. You need to ensure that your site stays updated CONSTANTLY, as well as checking your site after updates to ensure nothing broke. An even better method, crucial for complex/mission critical sites, is to do your updates in a staging environment first. Having a good scanner (I use Wordfence) is critical as well.
Besides the cost for a theme/theming system, you'll also want to utilize paid plugins for some features. Some, like Yoast SEO, are fantastic and free, but don't go willy-nilly on installing a bunch of freebies. You frequently get what you pay for.. Which is a hacked or broken WordPress site.
Keep all this in mind before you jump on the WordPress bandwagon. Sure, WordPress can do a lot, but it also requires you to put in the work, too. If you don't have the time or expertise to do it, you shouldn't use WordPress for your website.