I guess tanks are irrelevant, right up to the point where the enemy pitches up to the fight wrapped in them.
As an 'air' guy I can espouse how easily we can trash tanks these days. But in a theatre of ops where the weather and geography are against you and CDE is a concern then the mobile gun wrapped in armour looks a bit more credible. Tank warfare, as currently used in conflicts various, is very different to the days of old when they provided the punch for the troops to follow. Dismounted troops are often in the vanguard now, with tanks following behind to provide the HE-on-call after the find & fix stage. The tanks hide in buildings, under bridges and in complicated urban settings. The Fulda gap it is not.
If the logic about the viability of tanks and fighting vehicles is accepted then, by extension, any army formation is irrelevant - and I am not sure we are there. Again, as an air guy I can wince at how totally unprepared the British Army would be if it had to fight even for brief periods without total air dominance above. The last two decades has made the average British Army officer think of 'air' as the friendly domain that lives to support it. Once filled with airburst bombs and cluster munitions it will look very different, for a fraction of a second. Given how thin our true 'air dominance' capability has become I am amazed that the British Army has not seen fit to wrap itself in a layered and mobile GBAD system when it considers near-peer conflicts.