That's not the experience of many people. Or maybe, "taking the time to understand them" is not how they want to spend their time, and the mnemonics are bad because the use is not that frequent anyway.
Those same people spend more time joking about how complex the options are and linking that xkcd anyways.
It's an arbitrary set of command line flags and argument order.
So what's meant by "understanding" it, is basically "memorize".
Sure, if one devoted some time, they could memorize it. Like people can learn the PI to the nth digit.
But first, it's not just tar they use -- it's tens of other commands too.
Second, a lot of them have clashing flag order or slightly different names for the same arguments.
Third, most don't use them that frequently to make it worth it to sit and memorize it. Besides the infrequence of use means that simple memorizing once wont work, as they'll forget them without sitting down again later to refresh their memory. We can memorize complex vim commands because we use them everyday. Commands that we need once a month or once every 3 months, not so much.
It would be better for all if tar just did the obvious and intuitive thing.
And what is that obvious and intuitive thing?
Are you complaining about the need for a "-f" flag? If so, I'll agree, tar could take files the same way cat does. Tar's showing its age here, and would get a better interface without it.
But all the other flags are there for a reason, are the obvious mnemonic choices, and are the same ones used on other similar commands.
tar eXtract Ze File
tar Compress Ze File