Take this

Problem #1: There is no way that Imgflip's current userbase would be suitable for monetization. Most of the users are under 13 and cannot create an account here. Even if the user is +13 but under 18, I still think that they should not monetize their posts and templates until they get permission from their parents or they become an adult.

There is a solution, but it would require massive changes to the website. They will be highlighted in a separate comment.

Problem #2: How would Imgflip pay for the monetization of these creations? If all of these creations start monetizing, en masse, then Imgflip's expenses will rise far above their revenues. Now, there could be solutions to this, but you did not specify any.

My solution for that would be replacing your type of monetization. Instead of Imgflip paying for the earnings, they would show ads on the meme page and share the revenue with the meme creator. That way, memers and Imgflip could earn revenue together, resulting in a win-win scenario. The aforementioned separate comment will also solve this issue.

So problem #1 and #2 can be solved by implementing these ideas:
imgflip.com/i/89xgqs#com29104099
In short, it propose drastic changes to Imgflip's focus, changing from a funny meme website to a professional image hosting service with all the tools and assistance necessary in one place. The change would be so drastic that problem #1 won't bother anymore. Problem #2 could also be solved because the professional userbase is more willing to spend money for helpful tools.

In fact, your idea of template monetization is directly featured in this comment under the name of 'Licensable Templates'.The licensor (who made the template) would charge the licensee (who is using the template) with their license terms. It could also incorporate your interpretation of the idea, which are payments according to the template's popularity, as incentive bonuses paid by Imgflip themselves.

As for popular post monetization, I would not suggest that. In a reply to the linked comment, I proposed the removal of Imgflip's social and community components due to Imgflip's failure to grow their website as they focused on community features. Alas, you would not be able to publish images directly inside of Imgflip anymore. A moderator told me they spend a lot of time getting harassed by people who call them "leftists and rightists" who are "trying to silence people or whatever.", which signals that social features are not ideal for my business-oriented proposals because of the expenses associated with running a social media, and brand damage for future professional users.

I aint reading allat😭

TL;DR PROBLEMS:
1. Imgflip's users are too young.
2. Monetizing thousands of creations would make Imgflip lose a lot of money. Putting more ads and sharing the ad revenue instead would solve this problem.

Changing Imgflip's focus from meme website to professional image hosting service would solve both problems.

1 because Imgflip's young users will leave and adults will enter until both userbases reach stability.
2 because adults are more willing to spend than kids.

TL;DR MY IDEA:
I once suggested a similar idea to yours, but with professional focus instead of creator focus.

Monetizable templates would have the same concept as stock images, but it could also include meme templates made by the official accounts of whatever media the meme came from.

Licensing the template would go like this:
Template creator makes license, you pay for license.

Your idea of template earnings for each caption could also become incentive bonuses.

Creator memes would not be monetized because mod problems and professionals would be angry.

Template earnings:
50 captions - 0,49 USD
100 captions - 1,99 USD
150 captions - 4,99 USD
200 captions - 9,99 USD
250 captions - 12,99 USD
300 captions - 15,99 USD
350 captions - 19,99 USD
400 captions - 22,99 USD
450 captions - 25,99 USD
500 captions - 34,99 USD
(the limit is 500 captions, which means the template creator will earn 34,99 USD if their template got captioned more than 500 times)
Meme earnings:
10 upvotes - 0,49 USD
50 upvotes - 1,99 USD
100 upvotes - 4,99 USD
150 upvotes - 9,99 USD
(the limit is 150 upvotes, which means the user behind the meme will earn 9,99 USD above the limit, and they will earn on old posts too)
Meme earnings for views:
100 views - 1,99 USD
200 views - 4,99 USD
300 views - 9,99 USD
400 views - 12,99 USD
500 views - 15,99 USD
600 views - 19,99 USD
700 views - 22,99 USD
800 views - 25,99 USD
900 views - 34,99 USD
1000 views - 42,99 USD
(the limit is 1000 views, if the views surpassed the limit, the user behind the meme will earn 42,99 USD, the same thing is with old posts)

and what about other currencies?

Conversion rates: Exist

I doubt this is getting added, but what if it's someone like Iceu?

good question

they'll never do that 💀