In general, whenever we teach or learn something new, we start with the easy stuff then build on to the more difficult stuff. But this isn't always a good idea, because sometimes the easy stuff causes us to be stuck in a "good enough" situation.
When I started learning the harmonica, I learned to play with a "pucker technique", ie I covered the wholes with my lips. The alternative technique of "tongue blocking" (self descriptive, really), was just "too" difficult for me as a learner. So for a long, long time, the pucker was "good enough" and tongue blocking was too difficult for not enough reward. It limited my technique for a good number of years, and now that I can do it, I wish I'd learnt it years ago.
The same block of effort vs reward happens in all spheres of learning. If you learn something easy, but of limited utility, it's far too easy to just continue along doing the same old thing, and it's far too difficult to learn something new, so you stagnate. Harmonicas, singing, swimming, skiing, mathematics, computer programming; there's always the temptation to just hack about with what you've got rather than learn a new and appropriate technique.
This problem, unsurprisingly, rears its ugly head all too often in language learning, but with language it has an altogether insidious form: the "like your native language" form. If you've got a choice of forms, one is going to be more like your native language than the other, and this is therefore easier to learn. Obviously, this form is going to be "good enough", and the immediate reward to the learner for learning the more difficult form (ie different from the native language) isn't enough to justify the effort. However, in the long term, the learner who seeks mastery is going to need that form in order to understand language encountered in the real world.
The problem gets worse, though, when you're talking about dialectal forms.
Here's an example. Continuous tenses in the Celtic languages traditionally use a noun as the head verbal element (known as the verbal noun or verb-noun). I am at creation [of] blog post, as it were. Because it's a noun, the concept of a "direct object" is quite alien, and instead genitives are used to tie the "object" to the verbal noun. In the case of object pronouns, they use possessives. I am at its creation instead of *
Now in Welsh, the verbal noun has become identical to the verb root, and is losing its identity as a noun. This has led to a duplication of the object pronoun, once as a possessive, once as a plain pronoun -- effectively I am in its creation [of] it. This really isn't a stable state, as very few languages would tolerate this sort of redundancy, and the likely end-state is that the possessive gets lost, and the more English-like form (I am in creation [of] it) will win out. In fact, there are many speakers who already talk this way.
But for the learner, learning this newer form at the beginning is a false efficiency. There are plenty of places where the old form is still current, so unless the learner knows for certain that they'll be spending their time in an area with the newer form, they're going to need the conservative form anyway. To a learner who knows the conservative form, adapting to the newer form is trivially easy, but for someone who knows only the newer form, the conservative form is really quite difficult to grasp.
So teaching simple forms early risks restricting the learner's long-term potential. So while you want to make life simple for yourself or you students, make sure you're not doing them or yourself a disservice.