I was suprised to see Silverstripe is still a contender. I guess it all depends on what you mean by custom development. I still like cakephp when you're starting with a blank screen. WordPress is good if you're just doing theme tweaks and not straying too far from the idea of a basic CMS. Headless Wordpress can give you some flexibility.
I’d say it really depends on what you want to build. WordPress is great for a quick start and tons of plugins, but for fully custom solutions, people often go with Drupal or even Laravel with a CMS built on top. It all comes down to the balance between ready-made features and total coding freedom