I think there are several factors here
1/ the effectiveness of the tank depends on the effectiveness of your enemy.
If he is western, has satellite tracking of the battle field, air superiority. Drones, apache, shoulder launch capability anti tank then i would not want to be in a tank.
2/ The bigger argument here though is the Government does not want to spend out on more tanks so they will put up and excellent "tanks are so yesterday" argument.
This is mostly because our British army is leaning more towards a defence force and as a Island, tanks will struggle to breach our borders. so better to spend the money on defence against tanks than Tanks ?
The rest of Europe has land borders and quite frankly Trump was right...they need to stop relying on the US and The UK for defence.
End of the day its all about money and the UK wastes billions on defence. I remember the Jaguar fleet here, ageing ground attack aircraft that were given and new lease of life upgrade with helmet "look and shoot" tech costing millions and then scrapped the following year, the Nimrods that were 3/4 rebuilt and then scrapped on the factory floor, the Harriers given new engines to work in hot climates, upgraded to GR9 and immediately scrapped and then this week we read that the entire C130 fleet that has just undergone a main centre section wing replacement to keep them in service till 2033 have now been scrapped less than a year later. As for the UK's new Ajax armoured vehicle programme that has now been shelved again because it doesnt work at a cost of £5.5 billion ? that barely scratches the surface.
Lets hope the US doesn't give up on the F35 program or we will have to carriers with no aircraft
i could go on