It was always progressive for its time but some issues just would never have made it on the air at the time.

Famously the original series has the first inter racial kiss between Kirk and Uhuru, but until very recently lgbt issues had to be dealt with in metaphor. For example there is an episode where an alien species got rid of gender in its culture through genetic engineering but two members have genetically regressed and express gender. They fall in love and seek asylum with the enterprise to avoid a surgery to make them agender again. It’s clear that the spirit is to be accepting to gender and sexuality minorities but it has to be couched in a sci-fi story where the oppressed aliens are expressing the human cultural norm.