I have read similar views on Meghan's longevity as an actor in other places.
I think there is a misconstruction regarding acting as a career. In the US anyway. Success is not measured by whether you hit the (so-called) A-List, though it may for 'John Q Public'. That's all very nice if such happens but it is not necessarily a goal. Longevity as a character actor (sometimes morphing into Voice Over) is a valid career path (and usually far more interesting, in my view). Sometimes one gets involved in other aspects of the industry, like writing, or starting one's own production company, buying up scripts, etc., all of which starts to flesh out one's career path. (I see the same narrow lens used to judge Cressida Bonas' acting career: people tend to have a 'romanticized view of 'success', egged on by films such as 'La La Land').
Contrary to opinions expressed occasionally, the series 'Suits' surviving for 7 seasons (now going on to 8 seasons) is considered a very respectable run. It is a successful show. Meghan (as well as others in that show) would have had (as they will have) innumerable career opportunities to consider with such a solid series under her/their belt.
As in everything, it's all in what you make of one's choices and as far as I can tell Meghan was positioning herself for the long game (with her blog and fashion lines and charity work). Marrying Harry has been a drastic reversal of some carefully laid plans and considered initiatives. It's why I think Harry was a curve ball: Meghan was not looking to 'escape' into a marriage. This marriage does not 'save her' from a dull and dreary life prospect. It radically alters her plans and I am impressed that she has been willing to make the change. Suggests to me that there is something very 'real' happening between Harry and she.
Different perspective.