I mean, the first two sets they won 2/3 maps they put him in for (Junkertown x 2, Illios). Can't say he's specifically to blame.
If you look at the actual results, it went like this:
They lost a super-tight series to Dynasty, a great team.
They were convincingly ground out by Valiant, a very good team.
They got rolled by Outlaws, a low-mid-tier team.
That looks a lot like terrible, terrible tilt. Seagull can't be the cause of all that.