That doesn’t stop the cartels, not by a long shot. Ending prohibition in the US didn’t eliminate the organized crime families in the US, it just moved them to different areas of corruption. If it’s not alcohol, it’s drugs. If it’s not drugs, then it’s gambling, tax evasion, prostitution, loan sharking, organized theft, and so on and so forth. And without correcting the underlying issues driving alcoholism and drug addiction in the US–particularly poverty–complete decriminalization would lead to huge problems. Has led to huge problems in some cities.
While decriminalizing drugs would help to a degree, you need to correct the underlying problems that have allowed cartels to amass so much power in the first place, like weak governments, lack of opportunities, and high rates of poverty.