Meaning that some money that might have bought bitcoin will instead buy Coinbase stock,

That's like arguing against mining stocks in the precious metal community... nobody does that

I think Coinbase going public would be really bullish for Bitcoin, because a lot of people might join who dont want to directly invest in crypto but wouldnt mind investing in a company in the Cryptospace. And when Coinbase is booming we will have more people asking/knowing about BTC and other Cryptos.

Edit: Can you get the Compound/Lumen in those links? It seems like nobody with an existing Account can.
https://coinbase.com/earn/comp/invite/8x4vqjm3
https://coinbase.com/earn/xlm/invite/tx1r2c40