Nicely implemented chat services are in demand, or so it seems. They might be sold into the billions and monetized with ads, and I guess the negative spin comes from purely business origin, though disguised as concerns of crypto professionals.
BTW, if Telegram crypto was that much insecure why members of the so-called "security community" haven't yet compromised the Telegram chat for real (regardless of any contests and petty rules) and proven they had been right?
I don't rule out this as impossible - I just think that without such proof it's all just a kind of stupid whining.