I am not convinced
Doctor Who has any real ratings problems. I looked up the ratings for Series 1-11, and the average and median ratings are as follows:
- Series 1 (Christopher Eccleston): Average 7.95 / Median 7.97
- Series 2 (David Tennant): Average 7.87 / Median 8.05
- Series 3 (David Tennant): Average 7.68 / Median 7.46
- Series 4 (David Tennant): Average 8.42 / Median 8.07
- 2009-2010 Specials (David Tennant): Average 11.45 / Median 12.04
- Series 5 (Matt Smith): Average 7.73 / Median 7.57
- Series 6 (Matt Smith): Average 7.84 / Median 7.56
- Series 7 (Matt Smith): Average 7.83 / Median 7.57
- 2013 Specials (Matt Smith): Average 11.97 / Median 11.97
- Series 8 (Peter Capaldi): Average 7.26 / Median 7.06
- Series 9 (Peter Capaldi): Average 6.31 / Median 6.08
- Series 10 (Peter Capaldi): Average 6.22 / Median 5.92
- Series 11 (Jodie Whitaker): Average 8.39 / Median 8.06
- Series 12 (Jodie Whitaker): Average 5.99 / Median 5.80
So for the first eight seasons,
Doctor Who was hanging around in the 7s and 8s. For Series 9, 10, and 12, it's been hanging out in the 5s or 6s, with Series 11 (Jodie Whitaker's premiere season) as a higher outlier, along with the specials years being higher outliers.
To me that doesn't look like it's a show that's in trouble. It looks like it's a long-running show that has found a fairly stable equilibrium even as the television market has changed dramatically. The ratings are lower than they used to be, which is to be expected, but they seem pretty healthy to me.