Is use of sha3 justifiable? Is sha3 better than sha2 in (m)any aspects?
P.S. I want to use hashing for passwords in a database
Is sha3 better than sha2 in (m)any aspects?
SHA3 is built on-top of a fundamentally different construction than SHA-2 which has many nice properties. So yes, in many hash-function relevant aspects it is indeed better. As for password-hashing, SHA-3 implementations (without hardware acceleration) also tend to be slower, which is good in this case.
Is use of sha3 justifiable?
NO. Do not use a fast hashing function for password hashing. Use a dedicated password hashing scheme (PHS) such as Argon2 or bcrypt. These have been heavily reviewed, analyzed and even been built around the idea of being used for password hashing. They do their job really well and give you and your users the best possible security to the standards threats that you have to deal with when handling passwords on standard modern CPUs with fast RAM access.