Can keep as a backup if you want. I have one MTNL just incase my primary Airtel goes down due to some issue.
Believe it or not, voice quality has actually improved on MTNL. Could be due to majority users shifting to other networks. Even Trai mentioned in its report about good call quality.
Btw, 4g won't be starting atleast till June 2021. Because to check proof of concept (if telecom using gears from Indian vendors) govt needs 6 months for verification. Talk about minimum govt..
According to the latest TRAI report, BSNL stood as the top wired broadband service provider with 78.5 lakh subscribers in the country. In terms of wireless broadband services, BSNL added 159 lakh subscribers as of August 31.