Is 45 too late to change careers completely?

The people who struggle are the ones who try to erase twenty years and arrive as a blank slate. You are not a blank slate and you should not want to be.

Find the part of your old work that transfers. Operations, judgement, knowing how organisations actually behave under pressure — these do not expire. Then change the surface around it.

That is not a smaller move than starting over. It is the move that works.