From what I’ve heard, the reason why the devs put things behind a pay wall is because it required servers (which they need to pay for) or other reasons. Here are the possible reasons for ‘pro features’:
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“Remove "imgflip.com" watermark when creating GIFs and memes” - I don’t really understand why this is paid but people should be able to know a good, easy-to-use meme generator like imgflip
“Disable all ads on Imgflip (faster pageloads!)“ - Ads keep imgflip running. Without them, the devs can only get money from pro users (which isn’t enough to sustain the website)
“Max frames per GIF, Max Dimensions, Max Total Resolution (Frames × Width × Height), Max Video Segment Length, Sound on GIFs, Max Dimensions, Max GIF size you can store on Imgflip“ - All of these requires a bigger server (which means more costs)
“More Custom icons colour and grid” - I’m not exactly sure why but I think it requires servers to make them work (maybe more things need to be loaded)
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From the reasons above, there shouldn’t be any excuses for an undo button to be a ‘pro feature’. I really don’t think it requires a server or money.
Your comment might been a joke but I’m saying this so that everyone else might understand.
Caption this Meme 
