You say there will be less tanks so you don't need to bring long range AT.
So how will you deal with 5 razorbacks, 3 dreadnoughts and 2 storm ravens when you switched your army to deal with infantry "because there wont be enough tanks".
Meanwhile those tanks safe from your anti infantry fire while they shred your infantry just as hard.
Yes tanks are easier to kill with AT fire but unless you still bring said AT fire they are just as survivable and there ability to kill isn't diminished.
People talk about changed metas but due to the nature of tanks and there immunity to small arms fire bringing less AT is very dangerous.