Its worth noting, that Klopp's two biggest signings have yet to kick a ball for Liverpool. Thus far, under Klopp, Liverpool have spent not so much compared to United (its night and day looking at net-spend).
With Keita and Van Dijk, who will join in July and January respectively, only then does it start to match what Mourinho has spent. Unlike Klopp however, he has brought silverware, which, now Klopp has to do given the phenomenal backing FSG have given him.
Now that Klopp has got his 4 big targets (Salah, AOC, VVD and Keita), if he doesn't get CL consistently this year and next + one or two cups, and a good shot at the titlle by next season, big, big questions need to be asked, because he has been backed like no other Liverpool manager in history.
I think Mourinho is doing a good job at United, and that City's phenomenal season is making people lose perspective (fans, media). Just because someone is doing a B+ or A- job doesn't mean its suddenly a C due to another guy doing an A+ job. Its worth considering progress isolated from the competition sometimes. At the same time, if you look at the competition, at worst, United will finish 3rd this season. That's great progress when you look at the starting points of the cohort of the top 6 when Jose took over.
Finishing outside the top 4 would be disastrous for Klopp given the investment for this year itself. He's done a good job given the resources and the relatively mediocre spend so far compared to the competition. That's gone out of the window this year, and now the expectation changes for me, and for many other Liverpool fans, I'm sure.