I find it hard to explain that even though they are not passive, they still use the "to be" conjugations, and a writer would want to limit the usage of those constructions, but I cannot tell them why, and then add that they also may find those constructions effective in certain contexts.
I'm not an editor. I'm not even really a writer anymore (since I don't write). But I'm a reader, and I've hung out on message boards and have seen what "should-limit" advice can do to a text. Very early on it may help; later on it may become a source of unfounded anxiety. What this boils down to in practice is this:
Because some do it "too much", everybody should be told to do it less.
For a lot of people, that's unneccessary busywork, and for some it's downright desastrous to go down that route, because it estranges them from their own style. The problem doesn't really lie with the advice itself; it generally lies with the way it's phrased: as prohibitive. Don't do this, don't do that. They may only be guidelines, but that way, rather than getting the idea that - if you work on some aspects here and there you can get even better - you get the idea that if you're not careful, you're writing's going to be bad and nobody will want to read it. How many threads on websites start with "is it okay to...?" It's depressing really. Try it out, see if it works. Play around with it. See what else you can do. But don't stigmatise the majority of your toolset, because it's not going to result in short, sleek action sentences.
As for the grammar:
"The house
was quiet; too quiet."
"...the truth
was that I hated Christmas."
"Was", here, functions as a linking verb, linking the subject to a predicative adjective in the first case and to a dependent clause in the second case.
Predicative adjectives are fairly common in fiction, and "to be" is the most common way to introduce them. Other linking verbs might give more flavour "the house seemed/felt quiet", and then there are complete outliers that draw attention to their own stylishness, like "The house: quiet, too quiet." There are plenty of options.
If you're going for something more active, you could for example personify "the silence", and write something "Silence engulfed the house...", but you'll usually end up with more pathos that way. A lot depends on the general style of the text.
"...was that" constructions are rarer than predicative adjectives. When they do occur, it's usually in stock phrases such as "the truth was..." in your example. There's little to say about that: when it's okay to use them in real life, it's also okay to use them in fiction. But they're not going to be the spearhead of your style's literary appeal. However, you can't underestimate the effect of "downtime" in your text, and this is where such expressions shine, or rather where their failure to shine gives your readers a chance to catch their breath.
"My mother
was not satisfied until I tried on the fruits of her labor."
This could be read as another instance of linking verb + predicative adjective, but it's also the one example that can be read as an instance of passive voice (the active version being something like "Nothing satisfied my mother until..."). In this case, a lot of the things I said about predicative adjectives also imply; it's not really the posterbook example for the anti-passive-voice prejudice, and I'd rather not go into it (it's the first one that surprised me with its existance and has remained a special irritant ever since).
"I
would never see a dime from my brother."
A modal auxiliary verb; "would" is here used in its function as future-in-the-past. It's the past tense of "will"; but while "will" is usually a prediction ("I will never see a dime a from my brother" - surprise is unlikely but possible), "would" is in the past, and the event has already failed to occur. Modal auxiliaries are important to express various modalities (prediction, possibility, etc.). You can write a story without ever resorting to one, but there's really no reason to restrict yourself like that.
"Michael
was spending time alone with Dad."
The past continuous is smilarly pretty common, but fiction has somewhat less of it than other modes of writing. A lot of what you would normally say in continuous you'll say in a simple tense in fiction. For example: You've just woken up, and you're looking out of your window. You're not very like to say "The sun shines." You're using the continuous: "The sun is shining." In fiction, sencences like the "The sun shone," are fairly common, even if you're not just recounting facts, but are trying to weave a string of images.
However, sentences like "the sun was shining," is also fairly common. I think it was Geoffry Leech in
Meaning And the English Verb who said that the difference between the simple and the continuous aspect in fiction is one of foreground and background. If you use simple tense, then you're drawing attention to what's happening, but if you're using the continuous aspect, you're setting up expectations that something else soon going to happen (because the continuous aspect expresses duration, it's often used to frame events: "We were eating dinner, when the clock fell from the wall.")
"I
hate to shop for Christmas gifts."
I'm not quite sure why this is on list. Show, don't tell, maybe? Saying what we mean in plain words is not a bad thing, and neither is expressing attitudes, I think.
Ideally, studying grammar should expand your toolset by making you more conscious of what you can do with it. That's not going to happen if all you get out of it is the correct terms for things to avoid. And that's a very real danger. The key point I intend to make with this post is not that you shouldn't criticise things. But it's my experience that if you show a writer what they CAN do instead, they get excited and start experimenting, but if you tell a writer what they should avoid if they ever wish to be published they get to anxious to experiment. And if you don't experiment, you're not going to find your voice.