The linked article illustrates some relatively simple techniques to build a full-text search engine based on PostgreSQL.

Integrated functionalities may not have the exact same feature set of specialized tools like Elastic- / Opensearch and others alike. However adding new tools to your tech stack will make working on your product a lot harder than just sticking to what you've already got. Even though it may not have the same final high-end potential, it may serve you well for an extremely long time.

Stick to what you've already got. Appreciate a low amount of components. Keep it simple.