And zero profit nor viable plan to generate any. That's the problem.
There's no money to be made in being a message bus, certainly not enough to justify such a valuation and sustain hundreds of employees (whether it needs those is a different matter, but that's out of scope).
Discord's current business model is "growth and engagement" - this is what netted them their current funding and valuation. This requires keeping the audience captive and being able to regulate their behavior, including coercing them into doing things against their interests such as seeing ads, navigating through dark patterns, etc.
Having a healthy developer ecosystem goes against this - it means you become a dumb message bus and people will be able to automate their way around any inconvenience you might put to monetize them. Developers are great when you've got a real business providing a real product people pay for, but when your only bet is on the "attention economy", the last thing you want is to have "smartasses" around that can create technical workarounds to your inconvenience-based business model.
I just hope it's viable when you're taking VC money.
What do you mean? You can literally link to an image and Discord will replace that link with an inline image. And with opengraph Discord will embed youtube videos and twitter image and videos right into the chat.
They went from 5 Million revenue in 2016 to 120 Million in 2020. That's very far from zero or a lacking plan. The money is coming, it's just has not grown enough yet.