Decriminalization is akin to a parking ticket, it's still illegal, but is not a criminal offense. It literally is what the word means, not a "spin word". Both things serve very different purposes.

You still support crime syndicate with your money. You still have to deal with shady characters in the dark streets. You still have no clue what you are buying, the potency, what is it mixed with. When you travel, you have no clue where to go.

Decriminalization is a half-assed step from horrible situation, but its still a bad and unfair situation. We can do better once we recognize that some substance is not the end of the world (like weed recently).

Personal example - a friend brought from US a vaporizer with weed oil inside. Its much less health-damaging compared to usual smoking - even compared to plant vaporizers, the potency and effect is predictable, you know what to expect. This is how things improve when market is legal, in just couple of years. And this product is illegal everywhere else, including Amsterdam...

Portugal decriminalized possession, sale is still illegal. Overall usage dropped down. Decriminalization doesn't serve the same objectives as legalization. Pretty sure outright legalizing meth wouldn't be such a great idea.

Legalization is not the solution to everything either. Since weed has been legalized around here (Canada) a couple of big cities moved to literally ban smoking it everywhere. Current Quebec government is also pushing to ban smoking it outside province wide. They also let landlords ban marijuana use property wide. So basically, in these cities (and if the current Quebec government gets its way, which it definitely might considering its a majority government), marijuana is now legal to own, but renters now can't legally smoke anywhere.

Not really, it confers some pretty specific policy changes (making possession legal, as well as retroactively expunging records, is one part of decriminalization.)