Which description? That Wikipedia article says "The aim is to provide an alternative to centralized platforms such as YouTube, Vimeo, and Dailymotion."
The ambition remains to be a free and decentralized alternative: the goal of an alternative is not to replace, but to propose something else, with different values, in parallel to what already exists.
They're saying they're not a "replacement" because it's a decentralized alternative to something centralized. Not because it can't serve the same needs for technical or economic reasons.
https://en.wikipedia.org/wiki/PeerTube
Which description? That Wikipedia article says "The aim is to provide an alternative to centralized platforms such as YouTube, Vimeo, and Dailymotion."
They're saying they're not a "replacement" because it's a decentralized alternative to something centralized. Not because it can't serve the same needs for technical or economic reasons.