וַיֹּ֣אמֶר הַמֶּ֔לֶךְ מַהֲרוּ֙ אֶת־הָמָ֔ן לַעֲשׂ֖וֹת אֶת־דְּבַ֣ר אֶסְתֵּ֑ר וַיָּבֹ֤א הַמֶּ֙לֶךְ֙ וְהָמָ֔ן אֶל־הַמִּשְׁתֶּ֖ה אֲשֶׁר־עָשְׂתָ֥ה אֶסְתֵּֽר׃
Then the king said: 'Cause Haman to make haste, that it may be done as Esther hath said.' So the king and Haman came to the banquet that Esther had prepared.
The first party made by Esther was a full meal, the proof is that it says "Esther made/prepared". If it was just wine, the Passuk wouldn't say that.
משתה could be with or without wine.
As by Avraham there wasn't wine yet called "mishteh" - וַיַּעַשׂ לָהֶם מִשְׁתֶּה וּמַצּוֹת אָפָה וַיֹּאכֵלוּ - He made them a feast, and baked unleavened bread, and they ate.
As by Pharoah there was wine yet called "mishteh" -
וַיַּ֥עַשׂ מִשְׁתֶּ֖ה לְכׇל־עֲבָדָ֑יו וַיִּשָּׂ֞א אֶת־רֹ֣אשׁ׀ שַׂ֣ר הַמַּשְׁקִ֗ים וְאֶת־רֹ֛אשׁ שַׂ֥ר הָאֹפִ֖ים בְּת֥וֹךְ עֲבָדָֽיו - he made a feast for all his servants, and he lifted up the head of the chief cupbearer (wine) and the head of the chief baker among his servants.
Regarding משתה יין it is specifically a wine event.
After the Main meal there is a Banquet of Wine. This is When the conversations between The King and Esther happened. (both days).
It would also make sense, as it is not proper to speak during the meal. Especially a King. (The Gemarah mentions it as well for health related reasons)
וַיֹּ֩אמֶר֩ הַמֶּ֨לֶךְ לְאֶסְתֵּ֜ר גַּ֣ם בַּיּ֤וֹם הַשֵּׁנִי֙ בְּמִשְׁתֵּ֣ה הַיַּ֔יִן -
And the king said again unto Esther on the second day at the banquet of wine
Now back to your question:
Rashi is rather explaining the Root of the Word, For you information. As Rashi always does.
How it's used, is another story. As it's used for all food events wine and not wine related, hence the need to add the word היין when specifically talking about a wine event.
In fact Rashi is answering the obvious question, Of Why do we refer to a Meal Event as משתה, when it means to drink at the Root.