I'd say they are performing at almost exactly the same level as a 6th wild card does. The line between a .475 and a .525 team is almost invisible over any 10 game stretch, and they are still one of five teams projected to win between 83 and 86 games. It is still early. That could break three games in either direction.
And agreed it is the pitching. The line-up gets by when there is a good starting pitcher outing (including yesterday which was at least winnable). Without that they are still capable of winning games by scoring six or seven runs, but not as often, and probably not against the better teams. And if they'd just gone .375 in games with the fifth starter they'd have three more wins, instead they've gone 0-8.
And the bench players aren't really that bad for bench players. Clemens is actually doing well enough in that role (possibly as well as Hall will and better than Cave did in LF). Harrison and Guthrie aren't really markedly worse than Maton and Vierling probably, it's just that we know Harrison isn't going to get better and Guthrie hasn't been able to get going (and really shouldn't be playing the way you could justify playing Pache, purely for defense). In the DH era this is basically an all-utility player bench, with the best two guys platooning at 3B and 1B. It's just painful to watch those utility players get starts, but it always has been.
And JT is basically at his career numbers, and his 2021 numbers. We just take for granted he should be better and maybe he will, but given his age/position, maybe not.
The real loss to the bench this year so far is actually Stubbs. Last year that was one game a week where there was hardly any drop-off offensively and this year he is no better than Knapp was his last season.