I honestly dont think Horde is getting that much less content compared to alliance, but who am i to tell, i dont play horde, but trying to look on a very objective basis here, BFA was very much evenly split. Shadowlands was pretty much faction neutral, with some covenants focusing more on alliance characters and some focusing more on horde, and then the final content had a Cleaning lordaeron for the forsaken, which gave stuff to the alliance but was a majorly horde storyline.
Then Dragonflight is pretty much faction neutral as well, with the exception of the amirdrassil stuff and the retaking of gilneas, which are both just plot threads left from previous expansions that were addressed just so they can be free of them.
I’m not denying TWW has more alliance related characters at the front, but thats just the start of the expansion, and then we also have a expansion after that set in a horde capital, and if helping dragons protect a world tree that would become a night elf city is alliance content, then doing anything in silvermoon to help their people is horde content.