Uh, no. Dewott wasn't even in the Top 30 most popular Unova Pokemon list while Oshawott was tied at #8 and Samurott was at #24. Dewott isn't even nearly as marketable as Oshawott which is also evidenced by the lack of its merchandise; the only time you ever see a Dewott toy in Japan is when it's included in a set with Oshawott and Samurott. Meanwhile, those two have individual toys. They're the real money makers, not Dewott. ITT: Kids aren't here for Dewott and there are receipts to prove it.
Poor argument. For example Chandelure is at the top of that list yet it gets little to no attention from the anime staff. You're also missing my point, I didn't say Dewott was more marketable than Oshawott but that it looks enough like Oshawott that it can still be marketable with the right effort.
Dewott's lack of merch just means they haven't tried to market Dewott, it doesn't mean it isn't marketable.