Many founders we see are building on top of larger platforms and there’s a constant risk of “what if {platform} builds this?”
Some tactics for creating defensibility against this
Some tactics for creating defensibility against this

1/ Make your product exportable or interoperable with other/competing platforms. This is the one feature {platform} is extremely unlikely to ever build.
2/ Bundle value. Create a suite of products or features under one bundled price so that even if {platform} releases part of the bundle as a free feature, most customers will stay
3/ Build tools & support for power users. The most likely vector of risk is {platform} builds a 'good enough' + free version for most users https://twitter.com/louisnicholls_/status/1301517228043571206?s=20
All this said... "what if {platform} builds our product" is probably not your top concern as an entrepreneur at any given point. Sometimes you just live with the risk for a while and most of the time that works out fine.