How do we know that large scale anti gravity has been mastered by the Federation?
At least in the 23rd century, it apparently hasn't.
Otherwise, in "The Cloudminders" why were Kirk and Spock so impressed with the cloud city of Stratos with one of them saying
"the finest example of antigravity technology of its kind" or something to that effect?
If the technology was common place to suspend city sized objects in the atmosphere, then Kirk and Spock should not have been that impressed by Stratos.
At least in the 23rd century, it apparently hasn't.
Otherwise, in "The Cloudminders" why were Kirk and Spock so impressed with the cloud city of Stratos with one of them saying
"the finest example of antigravity technology of its kind" or something to that effect?
If the technology was common place to suspend city sized objects in the atmosphere, then Kirk and Spock should not have been that impressed by Stratos.