Are .fyi and .directory extensions worth investing in

Does these extensions hold any future? Any specific constraints that you know of, which may derail it's popularity in future or may dissuade people from buying it.

 

No.

Some popular country extension manage to fill a niche, .me, .io. for example. Do your research.

One thing that makes ngtld's unattractive, the best domains are held back by the registry with astronomical renewal prices.

 

Not really, I mean you need to have several potential prospects and great recognition of the extension outside the domaining bubble.