RG:
You referenced “Also Sh”t Tzitz Eliezer vol 17, s. 13.”
Looked, and found nothing relevant to the discussion.
In my earlier comment, I was stating clearly that with the exception of Chabad, no one supports the Divrei Torah as a substitute for Shlosh Seudos as a lechatchila. There can always be exceptions, and Erev Pesach is one example. Shabbos Teshuvah drosho is another. Here, it is bedi’eved. If you find additional exceptions, that would have no bearing on my point.
As for the Mateh Efraim noting that we cannot simply compare ourselves to Rashbi, that is essentially the Gemora (Brochos 36b) where it states הרבה עשו כרבי שמעון ב”י ולא עלתה בידם. One cannot always mimic the actions of a tzaddik. One needs to follow the instructions as found in Shas and Shulchan Aruch.