Note that the DEA schedules are all over the board. The current schedule system has barely any correlation with harm (see work by David Nutt). But we are also in a weird place where access to two of the most destructive drugs in real measurable effects - alcohol and tobacco - are legal.
At bare minimum we need to overhaul the schedule system, legalize drugs with low/moderate addiction potential (weed, psychedelics, ketamine, phenethylamines, the Shulginoids), and legalize everything in personal possession quantities, and for scientific/medical research.
High-addiction drugs should probably be medically gated in some way.
In fact, the "gating" of heroin through law enforcement is so poor that the difficulty and cost in scoring oxy once people face medical gating due to drug seeking behaviour is now one of the larger recruiting avenues to heroin use.
It's easier and cheaper for people to get heroin as a substitute than it is to continue to use a safer, cleaner supply of oxy.
If you want to medically gate these in a manner that does not increase harm it needs to be at the kind of level that e.g. paracetamol/acetaminophen is restricted in places like the UK (limits on quantity in a single purchase, but nothing that stops you popping to the next pharmacy over and buying more, or coming back the following day) or that e.g. some non-prescription drugs are sold (under the counter, pre-requisite information given out by a pharmacist and possibly some basic questions).
You can maybe push it to a non-aggressive push towards treatment, but if you start denying access you're right back to creating a black market you'll have no control over.
The exact threshold probably needs to differ per drug, but it the level of gating we're currently at even for legal prescription drugs like oxy is actively harmful.
Would caffeine and sugar also fall in this list?
Sugar, no, it doesn't bind to transduction receptors in the same way (it is rewarding, but not like "drugs" are).
I think the harm of legalization is only slightly below the war on drugs. Legalization means another vector of government control in my life, most likely outsourced to big pharma.
All the issues you are pointing can be solved by decriminalization are solved by individual responsibility and boils down to answering the question: Can you trust your source? If you can't answer the question you probably need help through a government sponsored damage control program.
To be precise, I used MDMA couple of times in my youth. My source sent every batch to a lab, we knew exactly what we were taking. Then he retired, and my MDMA use with him, cause I have no trusted source.
No amount of government control will substitute for cautious and responsible use. It might even hinder it, see alcohol, see tobacco, see opioid epidemic in the US.
But lack of legalisation also leaves drug cartels and murderous supply lines, high prices and reason to carry out crime to finance those high prices intact.
Even drugs like heroin should be fully legalised. Subject to prescription, maybe. But the harm from a clean, consistent heroin supply is vastly lower than the harm caused by the manufacture and smuggling alone, and decriminalisation of possession does not address that. Decriminalisation also does not address the cost issue which is a major problem with many drugs. A medical grade supply for a typical heroin user costs in the $10-$20 range (we know because e.g. the UK NHS buys heroin for hospital use; if you're given diamorphine for post-op pain, that's heroin).
But the biggest problem with the "drugs are evil" narrative is that it has damages serious discourse about which drugs are lower or higher risk.
LSD and psilocybin for example are certainly vastly lower risk than e.g. heroin and cocaine.
In fact, there's a famous case of a group of patients checking in after having snorted what they thought was cocaine, but which turned out to be LSD. Their blood levels suggest they would have ingested hundreds to thousands of normal recreational doses. They all walked out of there with no lasting harm.
In terms of other drugs, some drugs exists largely for time-limited circumvention of drug laws or because they're easier to create or smuggle, and would see their demands crash if less dangerous alternatives were legalised.