That actually hasn't launched yet. Telegram has announced it though and moved it to the test phase (https://promote.telegram.org/), but you're unlikely to see the consequences until a full rollout and even then it'll be marginal for the average user. So to clarify I don't think this will kill telegram or ruin it, but I do believe it to be a toxic choice for the community and a double edged sword at best for telegram themselves. You can see the effect this sort of business model has had on other platforms already. Spam and content farms for YouTube, Instagram, Etc. Additionally it's objectively not a good incentivizing pressure for quality features, community, or content. It in fact directly incentivizes one thing: More content designed to grab your attention faster produced by more people with now less altruistic and more questionable motivation.