Depends on what different people think. Given that Mourinho had spent 150 m+ on average over his time at United as of last summer, a better quality of football and a deeper CL run was certainly expected. The biggest gripe your own fans seem to have is the quality of football.
Now that Klopp has spent similar amounts, anything other than 80+ points, 2nd (at worst 3rd), CL QF and a strong domestic cup run will be failure. The scenario I mention is what I'd consider par, alongisde good football. Given United's similar overall investment since Jose took over, I'd say the same should be expected of Mourinho.
While the media are a bunch of lunatics, I do believe a better style of football would allow Mourinho a lot more breating room - it doesn't help that your ex players and legends say pretty damning stuff about the quality of football played. Sexy football and 81 points wouldn't have got the media reaction that Mourinho-ball and 81 points did. Regardless, that season with 81 points was certainly not a failure. Played to par in the league and bit below in the CL.
At the end of the day, trophies are king, but good football is important to some degree too. I can't think of a big in team in Europe that played the style of Mourinho's football last year - it was really dull. Now if a manager gets the same results playing better football, he will certainly get more leeway from the media and his own fanbase. Its quite logical. At the same time, Mourinho has lost the 'media darling' situation he had going on when he joined Chelsea in 2005. The media do target him unfairly at times - some of it he brings on due to his personality, but a lot of it is plainly unfair.
Happens though, they're (media) all a bunch of sheep. Benitez was labelled a failure for winning multiple trophies, getting Liverpool to be ranked 1 in the UEFA coefficients while spending far less than Ferguson, Mourinho etc. The narrative and expectations from him to win the league with the garbage he inherited, and less money to spend than his challengers was bewildering. I don't think his cold personality, or the bland football helped his case, either! At the time he was a figure of derision with United fans, especially when we brought up the spending argument - I think Ferguson being a demi-god skewed the judgement of your fanbase, and now you have to experience the harsh realities of being managed by merely very good managers, and realize, unless you're an all time great manager, its really hard to win the league without spending the most. I've gone on a weird tangent, sorry for that, but its still true ha!