Back in the days of using pre-made WordPress themes, the first step of the process was a trip to the theme store.
These Themes are designed to be one-size-fits-all. They come pre-packaged with tons of stuff that you don't need, adding unnecessary bulk to your website.
Once you'd purchased your theme, the next step was to upload it onto your website and try and make it your own.
These Themes aren't always easy to customize. Many of them have very rigid structures that you have to adhere to, and on some of them, simple things such as swapping out content are still a headache.
Inevitably, there will be a handful of tweaks that you want to make or features that you want to add that are outside of your theme's capabilities. To accomplish this, you'll need to hire a developer to implement these changes for you.
Implementing custom solutions on prebuilt themes increases the cost or difficulty of maintaining your website in the long run. Custom solutions can break when the theme updates, they can bog down your site's performance, and they increase the learning curve for everyone who needs to use the website.
Instead of fitting what you want into the constraints of a pre-made theme, start by planning out the exact journey that you want users to take through your website.
Every business has a unique story and unique selling points - planning out the ideal user experience will lead to a higher conversion rate than compromising for a pre-made theme.
A page builder is the modern replacement for a theme. It's a visual tool that allows you to build exactly what you want inside of wordpress.