I'm not sure that it really qualifies as "linguistic dumbing down", Giok.

Is there any logic or reason other than custom governing the idiomatic use of the present tense rather than the use of the participle?

After all, "I'm thinking ..." is pretty well interchangeable with "I think ...", "I'm hoping ..." wouldn't raise any eyebrows used instead of "I hope ..." and so on.

I'm loving ..." does sound unusual to an older pair of ears, however.