The introduction of DRS is a great way to reduce pressure from umpires as now decisions can go upstairs and chances of error are zero in that case. DRS is not welcomed in start by BCCI but with time they have embraced that change.
Zero? No way. DRS decreased errors for sure, but it cannot resolve every single error just like similar systems in other sports.Just think of the matches during the lockdown, we heard fake claps and cheer sound. Those are really bad and makes us stop watching the match. Commentary is needed, at times it might be worse. Just ignore the worse and enjoy the rest. 
I can understand why they take a lot of time sometimes as you mentioned, but what I don't like is the fact that they waste time checking pointless stuff sometimes when they don't need to.