I think you should do what you enjoy personally, but the advice I'd give depends on your personal goals. Do you want views and subs for the money, or to find people who enjoy the same things you do?
Because if money is the thing you originally set out to make, sure, change it up to something you think will be popular and attain a bigger audience.
But are you doing YT due to it being a hobby and because you want to make your own creation and something personal? Then you shouldn't compromise what you actually enjoy making videos on for the sake of money. This is assuming you're enjoying what you make now and wouldn't enjoy as much what you plan to make to gain more subs.
That's how I see it.
I like to do review videos the most about TV shows. If I wanted to make far more money, the thing that's popular out there is "theory" (incorrect use of the word, hence the quotation marks) videos that speculate about concepts in those TV shows. I don't like these videos though, and I don't bother to make them unless what I discussed in a review was already considered a "theory" (in which case all I have to do is revise what I already said and elaborate on it instead of coming up with an idea from scratch. This takes relatively little time so I make new videos out of revising what I discussed in a review when applicable).
I want my focus to stick to reviews because that's what I enjoy doing and would rather converse with people about. However, if I cared about making cash and didn't have a preference for what types of videos I make, I'd surely be doing these "theory" videos to get the bucks.
So it all depends on what it is you want out of your channel.
My hope is given enough time, I can build/find an audience that enjoys what I do, instead of trying to appeal to those who have different tastes by catering to what they would watch.
