The problem here isn't with decriminalization-- it's with lack of commitment to what they originally replaced enforcement with. From that article:

"Experts argue that drug policy focused on jail time is still more harmful to society than decriminalization. While the slipping results here suggest the fragility of decriminalization’s benefits, they point to how funding and encouragement into rehabilitation programs have ebbed. The number of users being funneled into drug treatment in Portugal, for instance, has sharply fallen, going from a peak of 1,150 in 2015 to 352 in 2021, the most recent year available.

João Goulão — head of Portugal’s national institute on drug use and the architect of decriminalization — admitted to the local press in December that “what we have today no longer serves as an example to anyone.” Rather than fault the policy, however, he blames a lack of funding."

It was working great while they were committed to funding treatment programs and pushing users towards them.

> After years of economic crisis, Portugal decentralized its drug oversight operation in 2012. A funding drop from 76 million euros ($82.7 million) to 16 million euros ($17.4 million) forced Portugal’s main institution to outsource work previously done by the state to nonprofit groups, including the street teams that engage with people who use drugs.

>cuts funding >Decriminalization doesn't work ! >not shocked

Isn’t the whole point of decriminalization that we won’t have to spend as much money enforcing laws and locking people up? Funny how you never hear anyone sound the alarm about lack of funding in the early stages when everyone’s talking about what a success decriminalization is, only when the dark side of such policies start showing. “We knew this would happen all along!”

No that's not the whole point not even close , decriminalization works in reducing human suffering by using the money spent of emprisioning humans and spending it on programs etc .

Would you prefer to spend the money on arresting people and keeping a large prison population or would you rather spend money on rehabilitation programs? Either way you're going to spend money, but I think that the latter approach would help more people.

And the US is immune to such problems?

This, "but we'll do it better" argument seems to fall flat universally. Everybody thinks they can do it better, but nobody actually does...