Should early-stage startups build custom internal tools or rely on existing SaaS?

In our early days, we spent almost three weeks building a custom internal dashboard to manage customer data and subscriptions. While it gave us complete control over our workflow, maintaining that custom code eventually took time away from improving our main product. ​For our recent launch, we integrated third-party platforms from day one. Although we pay monthly subscription fees, our engineering team spends 100% of their time delivering value to our end users.

​At what point does building custom internal software make financial sense, or should growing teams always leverage existing solutions?