No, it's not just that you "can" extract argon from the air, it's that we do, a lot. It's widely industrially available. If Argon were a suitable replacement for Helium it would be used instead due to its vastly lower cost, wider availability, and easier handling.
From this we can conclude that Argon is not a suitable replacement for the current uses of Helium. People pay a premium to use Helium today, and that speaks to the fact that Helium has unique properties that are highly advantageous.
He costs $3 per m^3 on the open market. Argon costs about $8 per m^3. N2 is cheaper.
There are some uses for He that are harder to replace. Argon will collect in low spaces more than He; N2 might be a compromise for welding. Nothing can be relied on to be quite as cold as liquid He. But there is a lot of substitution that can be done when He prices rise, several generations from now.
From this we can conclude that Argon is not a suitable replacement for the current uses of Helium. People pay a premium to use Helium today, and that speaks to the fact that Helium has unique properties that are highly advantageous.