This is an under-rated aspect; especially for plants, most experts in a particular genus will never find your observation if it is not ID’d to genus, or at least family. An expert in a genus will know at least vaguely almost everything it can plausibly be mistaken for (i.e., they might not know the right species but they will know the right family). Predictable (to an expert) mis-IDs are almost always way more useful than vague IDs (as long as you check your notifications and withdraw if you are corrected by an expert). So, in my opinion, it is ok and in fact highly desirable to be bold (as long as you are not intentionally being incorrect) down to genus for plants.
Here are some other examples of decent default IDs:
For birds, it is always sufficient to ID it to ‘birds’. That will 100% get it where it needs to go if it can be ID’d by inat users at all.
Most normal-is looking fish can be defaulted to ‘ray-finned fishes’
For centipede or millipede-ish things, go ‘myriapoda’ by default.
For worms, you may just have to go ‘animals’, unless you can tell if it is an annelid or have some worm knowledge.
For most other insects, it is generally sufficient to ID to ‘pterygota’ (winged and once-winged insects) if it belongs there, and being much bolder than that can annoy the insect people (and you can be wrong in ways you didn’t even know you could, like bees vs flies).
For most other invertebrates with some kind of legs, you can safely go ‘arthropods’.
For mollusks, you can probably just go to mollusks if you don’t know.
For fungi 
idk I just ID it to ‘fungi’ if I don’t know… I don’t get fungi (sometimes, you’ll still be wrong even then because it will be a slime mold you didn’t know about).
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