Telegram mining has indeed seen a decline as individuals are no longer interested in it anymore, and so many projects are currently struggling to keep users engaged. I think the token burn can be seen as an attempt to revive and make people have interest in it again, so many persons might even see this a trick or tactic, rather than a genuine move to improve the project. Even if they should burn more token i don't think it would be enough to bring back the decline in interest.