Idiomatic way to express "you bought an apple and complain it's not a pear"

Consider the following two examples:

• You're discussing a particular tablet. When you bought this tablet, you expected that you would not need your phone any more because you can call with the tablet, and while it's less convenient because it's bigger, you figured you don't call that often anyway. After a while you realize that, in fact, it turned out to be so inconvenient that you want to warn the other for this. At the same time you want to clarify that you don't want to complain about the fact that the tablet is too big (after all, this has other advantages).

• You read the memoirs of a particular sportsman in order to get somewhat of an overview of the culture in professional sports. After reading it you are somewhat disappointed because it only shows this for a particular sport / locale. You want to tell somebody that this book is not right if you want a general overview. But again you don't want to complain about this because you cannot expect a systematic overview from a memoir.

So in both cases you are disappointed with a particular aspect and want to highlight that, but without judging or blaming the author / manufacturer for this. I'm thinking about something along the lines of:

[I don't want to complain that the apple I bought is not a pear], but this tablet is not a good alternative for a mobile phone.
[I don't want to complain that the apple I bought is not a pear], but this memoir does not provide a systematic overview.

What would be an idiomatic way to express the part between brackets?

Here is a common way of putting it that seems to say it all.

"I don't mean to complain that I didn't get what I bargained for, […]"

The verbal form involving "bargain" is the phrasal verb "to bargain for"; its meaning can be checked here (Collins Cobuild).