What is the couchbase correct usage

i am not getting when to use couchbase bcz it is key-value json distibuted DBMS and in our project there is no accessing from key and every query is through N1QL only and if more indexes means more RAM it ll consume in index node and it is horizontally scaling only.so please clarify me what is the drawback of couchbase when i create more GSI indexes.

https://developer.couchbase.com/documentation/server/5.0/indexes/gsi-for-n1ql.html

we have used GSI in our project but that is not the ideal case to use couchbase ??..if indexes are increasing then index service node need to increase hardware capacity ??.is it better to use N1QL in limited ??