The Mechilta comments on the pasuk וְכָל הָעָם רֹאִים אֶת הַקּוֹלֹת:
רַבִּי אֱלִיעֶזֶר אוֹמֵר: לְהוֹדִיעַ שְׁבָחָן שֶׁלְּיִשְׂרָאֵל, שֶׁכְּשֶׁעָמְדוּ כֻלָּן לִפְנֵי הַר סִינַי לְקַבֵּל אֶת הַתּוֹרָה, מַגִּיד שֶׁלֹּא הָיוּ בָהֶן סוֹמִין, שֶׁנֶּאֱמַר: (שמות כ,יד) "וְכָל הָעָם רֹאִים"; מְלַמֵּד שֶׁלֹּא הָיוּ בָהֶן אִלְּמִין, שֶׁנֶּאֱמַר: (שמות יט,י) "וַיַּעֲנוּ כָל הָעָם יַחְדָּו"; מְלַמֵּד שֶׁלֹּא הָיוּ בָהֶן חֵרְשִׁין, שֶׁנֶּאֱמַר: (שמות כד,ז) "כֹּל אֲשֶׁר דִּבֶּר יי, נַעֲשֶׂה וְנִשְׁמָע." מְלַמֵּד שֶׁלֹּא הָיוּ בָהֶן חִגְּרִין, שֶׁנֶּאֱמַר: (שמות יט,יח) "וַיִּתְיַצְּבוּ בְּתַחְתִּית הָהָר." וּמְלַמֵּד שֶׁלֹּא הָיוּ בָהֶן טִפְּשִׁין, שֶׁנֶּאֱמַר: (דברים ד,לה) "אַתָּה הָרְאֵתָ לָדַעַת".
I don't think the point Chazal want to make here is to amplify the miracles that took place at mattan Torah or to amplify the greatness of G-d, as only He can perform miracles like those recorded here. As far as the first point, mai d'hava hava, and as far as the second, peshita, mai kah mashma lan. Chazal here (and as a general rule) have a didactic aim in mind. There is something we are supposed to learn from this midrash that we can implement.
You might be thinking, "How can this Chazal have anything to do with me? Do I work in a home for invalids? And even if I do, can I cure them?"
I submit to you that if you go to any shiur or listen to any derasha and look around the room, you will see plenty of examples of the "invalids" Chazal are speaking about. Or better, yet, most of us need only look in the mirror. How many times have we been חֵרְשִׁין, deaf to anything a rebbe or Rabbi is trying to tell us? Or סוֹמִין, blind to the words on the page in front of us because our attention is on our phone or elsewhere? Haven't we been אִלְּמִין, silent and afraid to speak out for Torah values, or חִגְּרִין, slow-walking doing what we are supposed to be doing instead of acting with zerizus. And last but not least, טִפְּשִׁין -- this one needs no explanation.
Ramban learns that there is a mitzvah to remember maamad Har Sinai derived from the pasuk “rak hishamer lecha.. pen tishkach es ha’devarim asher ra’u einecha.” That same pasuk is quoted in Avos (3:8) as the source for the issur of forgetting words of Torah. How can the same pasuk be used for both halachos?
As we once explained Ramban learns that the two ideas go hand in hand. If you truly remember and appreciate maamad Har Sinai in all its awesomeness, your learning is as different learning -- it becomes something that sticks in your mind and is unforgettable.
Tiferes Shlomo writes that this is what the gemara means when it tells us
רב יוסף ביומא דעצרתא אמר עבדי לי עגלא תלתא אמר אי לא האי יומא דקא גרים כמה יוסף איכא בשוקא
If there was no day of Shavuos, there wouldn't be other Yosef's in the shuk?! There wouldn't be other Yosefs, period! How would there be a Klal Yisrael?
What Rav Yosef meant is that if not for his awareness of that day of maamad Har Sinai every day, every single time he opened his gemara, he would never have become who he is. His learning would have been a different learning.
Chazal in the Mechilta are giving us a similar message. When you truly experience kabbalas haTorah and feel yourself as if you were standing at Sinai this Shavuos or any Shavous, then you're no longer deaf to the maggid shiur, you no longer slow walk your way to shul, you no longer are mute and can't answer when someone asks you what sugya you are holding in. And last but not least, you no longer go through your day and your life as a טִפְּשִׁ.

