A lot of what is said here is true, but it also depends on what your position is within the organisation - if you are senior (or a peer) and have the respect of

A lot of what is said here is true, but it also depends on what your position is within the organisation - if you are senior (or a peer) and have the respect of your colleagues then you can look at running a training session, followed by writing a piece of an application/a sprint using TS so that they can familiarise themselves with the reasons why it is better. Which is really the second part of this - you need to spell out why typescript will make their life easier/better. If you can't do that succinctly then it is unlikely that you will be able to convince them.