Women in combat is different in kind from the other professions you mention.
Women can do many support mos jobs in military as well as men, especially when in garrison and not deployed in a combat zone. Women as police officers can be very useful in domestic situations, undercover work, and as investigators. Beat cops, some can do it, but that is not the ideal role for a female.
Women firefighters are harder to justify just because the physical rigors associated with the job. I know one women who is every bit as good as her male colleagues as a firefighter. However, she is an Olympic level athlete, exceptionally strong and fit. Anyhow, police officers and firefighting can make some accommodations for females. If the position is suitable and the standards are equal, I don’t see how woman should be barred from those activities. Military units in direct combat cannot.
Women in the military have various costs; pregnancy, modification of equipment, lowering of physical standards.
Justifying having a entire group, or sex purely do support roles is inefficient, and directs resources. You can't take a female clerk, then send her downrange to lead a raid or ambush. You can with any male marine, the key is interchange, you lose that by having two sexs. Especially now that the battlefield has expanded.