So by your logic there should always be a draw between 2 Rinnegan users such as Madara and Sasuke. Both will keep absorbing and no attack will be fruitful. Also Rinnegan genjutsus don't work on each other. OK if you believe Rinnegan Madara = Rinnegan Sasuke
You say the tech has no limit but all techs have. Otherwise Kaguya would have absorbed Naruto's 9 TB Rasengan attack via Preta neg diff.
In fact all eye techs have a cost :-
1) MS :- User becomes blind
2) EMS :- Kill person with MS and take his eyes
3) Rinnegan techs :- Limbo can only use Taijutsu, Amino has a max range and a charging time.
All powerful jutsu have limitations . TSB can be attacked via senjutsu. 8 gates kills you neg diff. But you won't see this.
'Plot' did not nerf anybody. 'Plot' only failed (and by that I mean Kishimoto) to explicitly define limits of certain jutsu. 'Plot' forgot to restrict Yata and Totsuka. So by saying that Preta has no limits , you are actually acting like people who say Itachi can Totsuka Madara as its limitations are not shown. The actual flaw in the plot is not nerfing but specifying limitations and this failure of plot is leveraged by wankers to fap.