The biggest argument against total dismissal of the remake is the existence of remakes that, despite bringing nothing new to the table structurally and despite clear profit motive, manage to unambiguously improve upon the original.
The iconic example is Evil Dead 2, which is nearly a shot for shot remake of Evil Dead with the same lead actor and the same director — but with the benefit of a larger budget and more experience behind the camera; both Evil Dead and Evil Dead 2 are arguably adaptations of Equinox, with huge improvements to the script and pacing.
We might also consider as a candidate John Carpenter’s The Thing, an improvement over the earlier adaptation of the same source material but one that introduces brand new elements as made available by the technology: fundamentally, the difference between the 1980 film and the 2011 remake is that the 2011 remake exhibited poor craft. But, when we re-make overwhelming successes, we set ourselves up for failure: most factors that contribute to a film being well-received (beyond basic competence) are not predictable or controllable by any one person involved, and can thus be considered essentially random — in other words, remaking a successful film is like using your lottery winnings to enter another lottery.
Why do we see a greater frequency of truly successful remakes in horror than other genres? Because a low-budget horror movie can have low risk and high reward compared to other genres, and a slightly higher budget can result in huge increases in reception: within the entire low-budget range in the horror genre, the odds of making back your investment are pretty good compared to other genres and the stakes are low enough to encourage experimentation. A truly low-budget success can often be improved with an only slightly higher effects budget or the replacement of a handful of actors with slightly better ones, because a low-budget success means the premise and script are probably pretty solid (whereas the technical skills — the most expensive factor at that budget level — can be improved without changing out what works). A low-budget horror success probably makes, in total, a lot less than a high-budget success in any genre, and is successful with a smaller but more fanatical audience, so even a largely failed remake in this context is not just a good bet but a safe one too, the stakes being low.
The tendency to remake good movies is misguided; even though a remake of a mediocre movie is more difficult to advertise, it’s more likely to succeed, both in terms of improving upon the original and in terms of being profitable.