What would be the downsides of TypeScript, from your perspective?

In a large codebase, having typings, even basic ones, go a long way.

I don't know about the term static typing or if that's what really helps. I also annotate for readabilities sake. For instance, it's nice to know a variable in python is only intended to be 'ACTIVE' or 'INACTIVE':

    from typing_extensions import Literal

    ActivityStateLiteral = Literal['ACTIVE', 'INACTIVE']

    # Lower in the code, e.g. inside a flask view
    activity_state = ActivityStateLiteral = request.GET.get('activityState')

For TypeScript:

    type ActivityStateLiteral = 'ACTIVE' | 'INACTIVE'

    // e.g. react component
    const activityState: ActivityStateLiteral = props.activityState || 'ACTIVE'

That leaves me no doubt when I/a team member comes back 3/6 months later that I'm only dealing with 2 possibilities of what that variable can be (or should be). The intention itself also valuable, even if incorrect.