Refining the world rather than becoming angels

גם נראה טעם אמירת בני ישראל דבר אתה עמנו בהיותם יודעין כי נבראו בעוה"ז לתקן כל הנבראים ולא להיות ממש כמלאכים.

It also appears that the reason Bnei Yisrael said "you speak with us" is that they knew they were created in this world to rectify all the creatures, and not to be literally like angels.

When Bnei Yisrael asked that Moshe Rabbeinu serve as intermediary rather than hear Hashem directly, it was because they understood their purpose: to refine the physical world from within it, not to exist as disembodied angels.

שהרי יצאה נשמתן.

For their souls had departed.

At each utterance from Hashem, their neshamos left them — a sign that direct revelation was overwhelming their bodily existence.

ופן נמות ולא יהי' נגמר התיקון בעולם ונאמר על זה הטיבו כו' אשר דברו מי יתן והי' לבבם כו' וכתיב התם מי יתן טהור מטמא.

And lest we die and the tikkun (rectification) in the world not be completed — and concerning this it was said, "they did well in all that they spoke; would that this heart of theirs be theirs…"; and it is written there, "Who can produce a pure thing from an impure one?"

They feared that dying would prevent them from finishing their task of rectifying the world. Hashem affirmed that their request was right, and the Sefas Emes links the phrase "would that their heart be theirs" to the verse about drawing purity out of impurity — the very work of refining the physical.

והוא רמז שגם כאן הכוונה כדי להוציא יקר מזולל וזהו לבבם כמ"ש חז"ל על בכל לבבך ב' יצריך.

This is a hint that here too the intent is to bring out the precious from the worthless; and this is "their heart" (levavam), as Chazal expounded on "with all your heart (levavcha)" — with both your inclinations.

The doubled letter in "levavam" alludes to both the yetzer tov and the yetzer hara. The avodah is to extract the precious (holiness) from the worthless (the lower drives) — to serve Hashem with both inclinations.

גם הבינו בנ"י כי לא יכלו לקבל כל הדברות ויראו שעל ידי ריבוי האור יפלו ח"ו

Bnei Yisrael also understood that they could not receive all of the commandments directly, and they feared that through the abundance of light they would fall, Heaven forbid.

They recognized that the sheer intensity of the Divine light pouring forth at every commandment could overwhelm them and cause a spiritual collapse.

[ויש להרחיב בזה הדיבור כי קבלת התורה הי' בדרך מעשה בראשית אלא שסוד ה' ליראיו והמשכיל יתבונן במאמר חז"ל ע"פ (וישבר אותם) [*אשר שברת] יישר כוחך ששברת ואח"כ ניתקן בלוחות אחרונות ואם היו מקבלין כל הדברות מהשי"ת בעצמו הי' יותר קלקול על ידי החטא]

[There is room to expand on this point, for the receiving of the Torah was in the manner of Ma'aseh Bereishis (the act of creation); but "the secret of Hashem is for those who fear Him," and the discerning one will contemplate the saying of Chazal on the verse "(and he shattered them) [*which you shattered]" — "may your strength be straight that you shattered them" — and afterward it was rectified in the second luchos; for had they received all the commandments from Hashem Himself, there would have been greater ruin through the sin.]

In a bracketed aside, the Sefas Emes hints that Matan Torah paralleled creation itself. Moshe's shattering of the first luchos was praised ("may your strength be straight") and was ultimately repaired through the second set; receiving everything directly from Hashem would have made the damage of the Cheit HaEigel far worse.

לכן הטיבו כו' אשר דברו כנ"ל:

Therefore "they did well in what they spoke," as above.

For all these reasons, Hashem confirmed that Bnei Yisrael acted rightly in asking that Moshe receive the rest of the Torah on their behalf.

Summary: Bnei Yisrael rightly asked that Moshe be the intermediary at Sinai, because their mission is to refine the physical world from within it — drawing the precious out of the worthless and serving Hashem with both inclinations — rather than to exist as angels. Receiving every commandment directly would have endangered them and deepened the damage of sin; their request was therefore affirmed by Hashem.