Having a sustainable funding model for open source isn’t necessarily a bad thing IMHO. The potential upside here is that Sentry will be able to invest more into large improvements to the code knowing that their funding is sustainable. This is to the benefit of everyone who wants to use this software in the purest sense of open source, which is running the code on your own systems.
As they state in their article it's eventually OSS (after 3yrs it converts to OSS) and you're basically unaffected you're reselling a competing hosted version, you still have full access to the source code and can continue to run your own/modified version in house.
Given that Sentry is primarily the sole contributor behind improving and advancing their own product, making it more sustainable directly translates in being able to have more resources into making a better product whereas having their efforts stolen and repurposed by a competitive AWS/Azure hosted solution would directly make it worse. They'd be pouring their millions into competing against themselves whilst the cloud providers can use their marketing + monopoly network effects to reap all the commercial efforts off Sentry's investments.
The only losers here are the cloud oligopolies and Sentry's hosted competitors, Sentry ends up with a more sustainable business model they can invest in making a better product, which benefits their product and all their customers.
