SJD gets washed out a lot. Getting pushed 6 yards back and making a tackle isn't good D line play. Gaines is the inside guy and was getting good QB pressure and backfield penetration last season. SJD would do better at 3 or 5 than 1 tech.
You are not alone in a low opinion of Joseph-Day. OldNotDead shares that opinion, and has stated it frequently. However, I think you guys are in a minority here.
After a red-shirt season in 2018, I thought Jospeh-Day was very average (at best) in 2019. Thought your comments above described his 2019 play. However, last season, he was really good ... controlled blocks at the line, got off those blocks and made tackles within a couple yards of the line of scrimmage.
I have re-watched a bunch of 2020 games, and I did not see the player you described above.
Also thought Gaines was much-improved over his 2019 rookie season.