He's been too optimistic in the way he's setting up the team and on what he expects from many of these players, but maybe this is what he has to do now. We know Ten Hag is a very specific profile and he's working now without the needed tools. He can't buy a new team so he needs to evaluate these players under his demands to see how many of them could be useful in his system.
I guess he expected a better outcome in these first games, and if you get results there's no problem on testing and experimenting here and there, taking some risks and introducing new mechanics to see how the team responds. After two defeats now and strong teams coming next I expect him to adjust and be more pragmatic (like LvG did after Leicester, in his first games too) so we can start getting results and remove some pressure from the shoulders, and we'll expand our game again eventually.
Even before we kicked a ball under ten Hag I said here that I expected a trial and error kind of season. I didn't expect us to get battered that way against Brentford but I'm not surprised either. Not only the contrast between ETH and this squad is notorious in terms of profiles, but we come also from our worst season in ages (low confidence, frictions among players) with glaring holes in some key areas that we're yet to fix this window. All this in a league where every Joe has enough resources to punish weaknesses and mistakes so I counted on a rocky path here initially.
I think he has to realize what his best tools are, build a quick basis with some new additions and try to mask our flaws to restore some confidence and provide some stability during games. If Ole was able to survive two bad starts and finish 3rd and 2nd in both cases, and even a stubborn man like LvG managed to adjust his initial approach and get 4th, ten Hag should be able to revert from a bad start and deliver 5th or 6th at least after 38 games.
Top-4 would be really good and less than 6th should make us rethink, but I expect him to do the bare minimum at least. If there's been progress in the way we play and the atmosphere is good at the end of the season I think results could be secondary, but there needs to be a clear progression at least. We all can be reasonable but pressure and demands can't completely disappear.