It's a matter of balance. If the theme is too subtle, the reader may miss it. But if it's too heavy-handed, the reader will find it annoying.
I have read many stories where at some point I find myself saying, "Yeah, I get it, you don't like political party X. Do you have an actual story to tell or is this just a political rant?" Even when I agree with the writer's social or political or religious or whatever views, if it's too blatant it just gets tedious.
Old example but first thing that comes to mind: The Twilight Zone movie. There was a scene where a racist character is complaining because a Jewish person got a promotion that he thought he should have gotten. And there's this dialog where he's complaining to his friends about how "these Jews have all the money", and his friend says, "I know Goldman. He's not a rich man." He says he should have gotten the promotion because he's been with the company 10 years, and his friend points out that Goldman has been with the company for 15 years. Etc. Every argument he makes why he should have gotten the job rather than the Jewish fellow, one of his friends has a rebuttal. I hate racism and antisemitism as much as anyone, but in real life, surely the guy would have one or two reasons why he should have gotten the job rather than the other guy that were not quickly and easily demolished. I can believe the other guy won on 7 out of 10 points, but 10 out of 10 seems a bit much. And even if true, would his friends have really all sat there explaining to him why he was being a jerk? Surely his friends would be more likely to be saying, "wow, that's too bad" and being at least somewhat sympathetic. Maybe a "now Bob, don't get carried away".
If you reduce the people or ideas that you disagree with to caricatures, your story is probably less persuasive than if it was more realistic.