Initially, you grow like crazy and with great user reviews, as you're able to pick and choose the highest quality items.
Unfortunately, at some point you exhaust the supply at a given quality level, but your valuation mandates continued growth.
So you lower your quality requirements to obtain more supply, which only buys you a bit more time until you hit the next supply limit.
The only winning move seems to be stay private and accept there's a near-term cap on your revenue growth, after which you will grow much more slowly (at the natural supply expansion rate).