Genesis 24,63 says:
וַיֵּצֵא יִצְחָק לָשׂוּחַ בַּשָּׂדֶה לִפְנוֹת עָרֶב וַיִּשָּׂא עֵינָיו וַיַּרְא וְהִנֵּה גְמַלִּים בָּאִים And Isaac went out walking in the field toward evening and, looking up, he saw camels approaching.
The Gemara in Berachos 26b tells us based on the verse above that Yitzchak established Mincha:
יצחק תקן תפלת מנחה שנאמר ויצא יצחק לשוח בשדה לפנות ערב ואין שיחה אלא תפלה שנאמר תפלה לעני כי יעטף ולפני ה׳ ישפך שיחו Isaac instituted the afternoon prayer, as it is stated: “And Isaac went out to converse [lasuaḥ] in the field toward evening” (Genesis 24:63), and conversation means nothing other than prayer, as it is stated: “A prayer of the afflicted when he is faint and pours out his complaint [siḥo] before the Lord” (Psalms 102:1).
Obviously, Isaac was the first to pray as evening approached, at the time of the afternoon prayer.
The interpretation of לפנות ערב seems to imply it was towards evening, at the time that the sun is resting. And the Ibn Ezra says this as well:
לפנות ערב. קרוב מביאת השמש וההפך לפנות בקר ובפרשת כי תצא אבארנו באר היטב
This time would technically be viewed as dusk. And if that is when Yitzchak Davened, why don't we do exactly the same? At the same time that he did? Dusk in the halachic sense is called מנחה קטנה
Yet we are allowed to pray מנחה גדולה - about a half hour after halachic midday. Why is this allowed?
Many Yeshivos and Talmidei Chachamim Daven at this מנחה גדולה time period. Why? Is there not an extra מעלה to pray at the exact same time as Yitzchak did?