Lcanceling is like equipment load. You never want to be over encumbered, just like you never want to miss an lcancel. Sometimes you pick up too much, and are punished with having to throw stuff away, and if you miss an lcancel, you have more landing lag.
Lcanceling is work with pay, auto is pay with no work
This one is 100% subjective, but auto l canceling just sounds sloppy. Lcanceling forces you to react to when and where you are landing to respond accordingly, while auto allows you to not worry about that as much, except for spacing purposes.
Like I said before, some things can mess up your timing as well ( needles, fod, opponent reactions, etc.). Auto cancels these things out.
All I got.
Okay. Now, here is a honest critique of this post's argument as a whole.
Both of these analogies are flawed. The first analogy, the equipment load analogy, is flawed because being overencumbered in any game has had more than a minimal effect on gameplay. I go from being able to move at any steady pace I desire to becoming very slowed. That effect is not replicated by missing a L-cancel.
The second analogy puts an overemphasis on L-cancelling's value. If it's simple enough to become a natural reaction in the first place, and as you established in the first place a while back, that "it's not hard" (which no one has actually argued that it is in this thread as of yet to my knowledge, and I don't think would), then why make a comparison to work? It's not work, it's imbuing a natural reaction, a reflex, to a particular instance happening. If it were real work, people would note L-cancelling as having a more serious effect on gameplay when performing commentary. And yet, rarely ever, at any level of play including top level, regardless of the professionalism or knowledge of the commentators involved, do you hear things about this as if they're truly significant to the level of play that this is occurring. One might note that if this is at all levels of play, then perhaps its significance is potentially brought into question.
If you can explain that second analogy in a bit more detail than the one line, then perhaps I can see the picture you're trying to paint without having to make these broad assumptions backed by countless viewing hours worth of research.
In regards to L-cancelling forcing you to react, that is, again, producing a natural reflex to flick a trigger on a controller to something unconsciously. You must agree that if I'm spending time in a game against someone focusing my attention on hitting a particular button, regardless of its simplicity, I'm overlooking factors much more worth my time at that very moment.
Spacing is universally significant regardless of L-cancelling. You can L-cancel all you want, but if you do an aerial on shield and you're too close in range? You're going to get grabbed or punished for not spacing correctly.
You are correct that these projectiles can mess up timing, but these things you listed mess you up regardless of hitting a L-cancel. It is, to refer to previous points, the significance of fundamentals and mental play that makes the difference in results and not the press of one button, but many over the course of a match. Reducing the number of presses by the number of aerials you perform by switching on auto is theorized (not proven, but theorized) to have no effect on the overall outcome of the match in the first place.
On top of that, having automatic cancels does not make you untouchable.