Does כָּל בָּשָׂר refer to all humans or all creatures?

Summary: Ibn Caspi and Baal HaTurim diverge from the midrash.

Post: Towards the start of parashat Noach:

12. And God saw the earth, and behold it had become corrupted, for all flesh had corrupted its way on the earth.

יב. וַיַּרְא אֱ־לֹהִים אֶת הָאָרֶץ וְהִנֵּה נִשְׁחָתָה כִּי הִשְׁחִית כָּל בָּשָׂר אֶת דַּרְכּוֹ עַל הָאָרֶץ:

Ibn Caspi writes:

"All flesh: sometimes in Hebrew this refers to the class of living creatures, and sometimes only to people, whether all of them or some of them. And it is written (Yeshaya 66:23):

כג  וְהָיָה, מִדֵּי-חֹדֶשׁ בְּחָדְשׁוֹ, וּמִדֵּי שַׁבָּת, בְּשַׁבַּתּוֹ; יָבוֹא כָל-בָּשָׂר לְהִשְׁתַּחֲו‍ֹת לְפָנַי, אָמַר ה.

23 And it shall come to pass, that from one new moon to another, and from one sabbath to another, shall all flesh come to worship before Me, saith the LORD.

And also the word כל, all, in Hebrew, varies in its meaning, and this is known to those who are experts in Hebrew."

Ibn Caspi's intent, here, is to differ from Rashi, who had interpreted כִּי הִשְׁחִית כָּל בָּשָׂר אֶת דַּרְכּוֹ as the animals engaging in illicit interspecies sexual behavior. Thus:

כי השחית כל בשר: אפילו בהמה חיה ועוף נזקקין לשאינן מינן:

Ibn Caspi even (seems to) gives a different definition השחית, of more general misbehavior and misdeeds. And he seems to even say that it was not all of them. Perhaps, then, Noach was saved by virtue of being a tzadik and not just a non-sinner to that extent.

The Baal HaTurim says the same as Ibn Caspi about כל בשר being all humans on a peshat level, even as a later כל בשר in the parsha can refer to all living creatures. Thus:

ועל  דרך  הפשט  כל  בשר זה כל האדם,
 ולמטה  (פסוק יז־יט) מפרש  כל בשר אשר  בו
 רוח חיים, ומכל החי  מכל בשר, חיה  ועוף, אבל  כאן
 כל  בשר כל  אדם וכן  יבא  כל  בשר (ישעיה סו, כג):ש