Yes, I was able to access term store manager. The behavior is very weird. Today, when i checked again, term store management link is now available and I am able to create managed metadata columns. I didn't provide any extra permission or enabled any settings/features.
I've also seen this issue today on a demo tenant that I've provisioned. Managed Metadata service is running and has terms available, but can't use the Managed Metadata column type in a document library