Is RRC Inactive State required in 5G NR?

It can be, but is more targeted for mMTC / uRLLC use case.

Here is a nice video with straight explanation on RRC Inactive States in 5G NR:

RRC Inactive States in 5G NR
Source: Telco Bytes

Also check nice summary compiled by @vikas.nain here: Summarizing 5G RRC Inactive state and comparing with other 5G RRC states