Understanding ものだ to make general statements

Question

I'm trying to understand the use of ものだ to make generalised statements. I think I failed to use it correctly in this sentence (note that this question has a different emphasis from the link).

I'll start with a use of ものだ which I know is correct, so you can understand what I'm getting at:

だれでも新しくて便利なものに興味を持つものです

Suppose I want to make the statement that cats are not friendly. Here are my two attempts:

A) 猫が人なつっこくない。
B) 猫が人なつっこくないものだ。

What changes between A) and B)? Without further context if I say sentence A) will the listener start looking around for the particular cat I'm talking about? Or will they take it as a general statemement that I think all cats are unfriendly?

Is sentence B correct? In the linked question I was told to use 生き物 (in a different position) but I think that's because I was unclear in my question.

Answer 1

I feel a cat in sentence A is the particular cat. However I feel cats in 猫は人なつっこくない are all cats as a general statement.This is because of the difference between は and が.

So I feel your sentence 2 is unnatural because ものだ means "something everyone says generally". 猫は人なつっこくないものだ is natural. And you can use ものだ for creatures. For example, 赤ちゃんは、よく泣くものだ(It is said generally that babies often cry).