It doesn't work like that anymore. Go went from being worse than Kanto Ash to fighting a legendary alongside Ash (and also catching it).
Lol no, he caught Eternatus because wolves weakened it so much.
A Pokemon's strength is dependent on its trainer and since this Ash is stronger than all the previous series Ash, his Pokemon are also stronger.
Hahahhahah no. It doesn't work like that. Based on your logic Farfetch'd is stronger than DL, Incineroar,Charizard. Or his SM Pokemon are stronger than A-G, Infernape, Sceptile, Charizard, his Buizel since he's from DP is stronger than Charizard, Sceptile, Staraptor too. Then we have Goodra, Noivern being stronger than Charizard , Sceptile, I could go on. So this is wrong. Each of Ash's Pokemon have different power and uses different techniques and strategies. It's very wrong to say that all of Ash's Pokemon are equal in some series or say that all of his Pokemon are stronger than all Pokemon he used before. Imagine saying Rowlet, Buizel, Staraptor, Noivern,Farfetch'd etc etc are stronger than Greninja, Sceptile, Swellow, Krookodile, Incineroar etc.
He will soon be battling E4 level trainers and he can't have only two-three mons that can actually beat them cause then he would have no luck against Leon. All his current team members should be stronger than E4 level.
He can battle them and win with Pikachu or even Lucario. Just because Pikachu/Lucario win that doesn't mean Farfetch'd magically becomes that level.
No, his current team except Pikachu and Lucario shouldn't be stronger than E4 nor close to that because of other Pokemon's disrespect( which I responded why what you said about current team being stronger than Ash's older Pokemon make 0 sense) nor that makes anywhere much as sense unless it's a big time skip. Heck you can see that with Pikachu: Pikachu only would be able to take E4 level per say in XY , so it took him like over 15 years to do that, why would current Pokemon do it in a year... Lmao.
Not to mention that since we get Gary, Iris there's high chance Ash's older Pokemon return and if they do, they should battle E4 and Champions and not current team. Because, since DP they trained really hard and they have time and experience advantage thus that means power advantage over current team.(Charizard, Infernape, Sceptile, Snorlax, Gliscor, Swellow, Corphish) etc.
If they don't return we will likely get 1 on 1 with E4 so Pikachu will be used( or even Lucario). I am still pretty sure Aegislash until proven otherwise: is holding back against Farfetch'd or he's Wikstorm's non main battler Pokemon that WIkstorm is using against weaker opponents.