Army were technologically and tactically superior to the Argentinian counterpart though. The British Navy was a traditional world power and the Royal Air Force had tons of air battle experience. With the assistance of the US intelligence, Argentina did not stand a chance against the British during Falklands War, though they achieved some brief tactical victory.
It could be about the mental toughness but I don't think that the Argentinians had enough to engage in a large-scaled air/naval/land warfare. Argentina short of supply of anti-ship missile is further proof that Argentina couldn't sustain a long term war.
The world has undoubtedly changed since the Falklands War. However, the UK still possesses the capability to deploy its troops worldwide, War in Middle East for example. What has Argentina done to convince you that they can win a war against the British today?