Jesus Christ. That fact is only in your head luckily not in real life.
Why do people have to invent racial/sexist issues as the default answer to anything / everything nowadays? Instead of looking for more logical answers (to paraphrase Occam's Razor).
Number of black (or mixed-race) players in the PL (25% as at Dec 2021), total number of black players in professional football in the UK (7.8%) number of black players in the latest 25 man England squad 8 or 9 if you include Saka who departed with covid (32-36%) and for the last competitive England WC squad it was 9 (36%).
Maguire is Southgate's captain so regardless of current form he's going to give him some leeway (to say nothing of the fact Southgate is not a 'pick them on current form' manager.