As I understand, in English, when we are talking about something so close that we can (literally or figuratively) point our finger to, we can use "this".
This cake is great. (implies the participants are near the cake)
If we are talking about something that is not very close, or the place/time is not very specific, we can use "that".
That cake is great. (implies the cake is far away)
In my native language (Portuguese), a translation would be "isto" ("this") and "aquilo" ("that").
The problem is that there are many instances of English sentences using "that" that I would use "isto" in my native language instead. For example:
A: Let's eat some cake.
B: That would be great.
I understand that translations may not perfectly capture the nuances of different languages. My question is if using "this" would be OK in that instance. More generally, is English more lax regarding the use "this" and "that" ("isto" and "aquilo" are very strict in Portuguese).
P.S: my question is essentially the same one as this one, but the accepted answer does not really answers the issue of using both words interchangeably (I'm looking for a yes/no answer).