Those links don't work, but I checked op.gg.
First off, your grade is partially based on how others do on that champ. Since thresh is always popular and especially rn since he is meta, you have a lot of competition for getting an S.
That said, your KDA isn't all that amazing. 4-0-14 is GOOD, but not great (for an S). Same with that 5-4-28 (33 total is a lot, but that 4 deaths hurts a lot). Each death is pretty brutal when it comes to your grade from what I have seen.
Are you warding? I see you bought some pinks several games ago, but nothing in your past few. OFC, even if you buy a few pinks doesn't mean you use your sightstone. For reference, top players place about a ward a minute, so when you look at your vision score at the end of a game, check to see if your wards placed is close to the game time.