Two separate things, not to be confused...

The traditional airline career path began in the military. Both military and airlines have long career pipelines and you cannot jump in or out in the middle. Today's senior widebody Captains began their journey in Vietnam.

Society has changed, and the military has followed suite, but the senior pilots of today reflect a snapshot of 1970's demographics. What you see there is 40 years time-late, and does not reflect opportunities today. Both the airlines and the military are falling all over themselves to hire non-whites and women, when they can find them.

If you pay attention to the younger pilots, you'll see much more diversity but still plenty of white males. Reason for that is that aviation is a long journey and usually starts with childhood interests. White males are more likely to be rural or suburban gear-heads, and to pursue technical education relevant to aviation. Woman tend to prefer white-collar education and work to technical fields, so the pool of interested minority/female applicants is limited just based on their own interests. I don't consider that to be a fault of the aviation industry, if there's a problem maybe society needs to provide better early education opportunities to some demographics.

The majority of female pilots tend to drop out of aviation, or take career off-ramps to raise kids. Their choice, but entirely understandable...it's a rough lifestyle with kids.

As far as cockpit culture, with the few rare exceptions that exist in any walk of life, you'll find it very welcoming and open to anyone (we even have trans pilots now, although I can't say they are warmly accepted just yet).

If you're interested and willing to do what it takes to get there, you'll have a good experience. Although you'll probably have to discuss politics you don't agree with at some point, but all of us have had that experience.