Competition slides are tricky to handle.
The traditional magic quadrant fails to capture the true competitive landscape (the startup chooses the two axes, of course they’ll end up in the top-right corner).
Comparison tables are better suited as they highlight the key differences between offerings.
In the case of Opendoor, I’m not too troubled by the absence of a competition slide. They position themselves as buyers/resellers of property. In that regard, anybody with cash on hand or the ability to get a credit is a competitor. The business model relies on the availability of capital to acquire, the ability to negotiate a discount, and the ease of reselling, none of which seem overly impacted by competition.