I don't know how you can say that. Outside of 16-17 disaster, Varlamov was great for us. Arguably the only reason we were respectable as a team. Grubauer came in as a backup, so to me he was a clear downgrade to start from Varlamov.
I don't see how you can say great. Varly was great in one year, good in a couple others, and solid overall. Grubs also didn't come in as the backup... the org traded for him and gave him a 3 year deal at double the going rate for backups. He was brought in to replace Varly... Bednar just didn't trust him at the beginning.
If you go back year through year, you see that Varly is the starter, but beyond a stretch early in the Roy era... he really wasn't that much better than his backups.
18-19: Worse numbers than Grubs and lost the starting job
17-18: This was a good year for him. Better than Bernier... not by a huge amount though
16-17: Complete disaster, was out performed by Pickard and basically lost his starting job temporarily
15-16: Starter and had a solid year... but Berra and Pickard had better numbers
14-15: Good year and was the clear starter... Pickard was an unreal backup that year and Berra was solid
13-14: Great year and a year he should have won the Vezina with some Hart love. Giggy was clearly on the downturn.
12-13: Another pretty bad year, Giggy was better
11-12: Solid year, not great or even good. Giggy was better
IMO a lot of the Varly opinions function on him being absurdly good in 13-14 then playing solid for a bit under Roy (which his system inflated goalie numbers).