I think Celeste was popular enough in the indie space to get "big developer". To put some words in OP's mouth, its not "Big Developer" as in a large studio. But "Big Developer" as in well known and acclaimed.
In the article they make that 2025 is a tipping point where open source frameworks and libraries "just work", making speedy, fun development possible without needing to fight the clunkiness of heavyweight engines.
And any new stuff regarding Celeste or from their devs will forever be relevant to me! Highly recommend to any who haven't played it.