All of these "internal tool builders" don't excite me as much as the concept of a "saas building builder" - I think https://saasrock.com (bias since I'm helping) has unique potential.
They are very different use cases. Retool & the like are for building stuff used by yourself/your company. You can connect to internal data sources/APIs and build dashboards. SaaS builders are for building your app for a broader audience. They mainly offer features like authentication, user management, CRM, marketing, subscriptions, billing.