I'll watch it but I think the closer it's getting to contemporary times, the tawdrier it seems.
The first two series, with Claire Foy, seemed like more of a historical drama. Obviously a lot was invented or distorted, but not many of us have first hand memories of those times, so it wasn't so obvious. Plus, the sets and costumes were gorgeous. However, many of us remember the Diana days very well, and it just seems like televised tittle tattle rather than a dramatised insight into a changing world, and a young woman coping with the transition from princess to queen.
All that said, I will definitely watch the 5th season! Not sure about Imelda Staunton, but surely she can't be worse than Olivia Colman?