You are gonna argue Lovren was good pre-VvD?
He's not a bad player now, but his confidence was shot at that point. His clubs fans were giving him death threats because he was so mistake prone.
His (and Liverpool's) defensive turnaround begun after that infamous Spurs game, after which Klopp dropped his fullbacks lower (resulting in what some called more "boring" Liverpool) and the emergence of Robertson and TAA/Gomez (instead of Moreno and Clyne).
Up til then, Lovren and Matip were, yes, looking bad, but they were in no position to succeed.
Both went on to play great football once they got a run of games in non-shambolic team.(and Gomez as well)
By the time VVD came in during the january 2018 transfer period, the change in Liverpool's defensive scheme already begun.
Both Lovren and Matip were looking much better now alongside decent fullbacks in a system that didn't leave them out to dry so much, and VVD was the final cog to push now a decent defensive team to a defensive juggernaut.
And yes, at the time (Spurs game), I imagine Lovren's confidence was shot. Credit to Klopp, Lovren's teammates and Lovren himself for playing through it and having an absolutely immense 2nd half of the season, possibly being Liverpool's best player in the Man City CL tie and the CL final, as well as a great run with Croatia in the WC.
He's a VERY good CB. He's also got a positive attitude and apparently one of the leaders in the lockerroom.
The memes about his mistakes should've ended 2 years ago - yet they didn't.
Calling him "not a bad player" doesn't do him justice at all.