not my tweet or my fic (and there’s a good chance of this comment being a bot) but yeah, don’t do this. sure, some writers wouldn’t mind having fanfics (or direct continuation) of their fanfics written by someone else. some may even be thrilled and happy. but the fandom etiquette is that if you want to write a fanfic or a continuation of someone’s fanfic, YOU POLITELY ASK THE WRITER FOR THEIR PERMISSION. not their readers.
also 5 months isn’t long at all. 5 months is 5 minutes when it comes to fanfics. I’ve waited years for my favorite fics to get updated (one of my favorite fanfics was updated by the author after 13 years) and I’ve never said anything to them about “it’s been ___ years, I don’t think it will get updated anymore”. because another fandom / fanfic etiquette is that fanfic writers write for free in their free time, they don’t owe you anything. maybe they will update one day. maybe they won’t. if you want your favorite fic to get updated, you comment something like “this is good!! I’m excited for what happens next” and maybe your positive comment will motivate the author to update. but you don’t say “it’s been ___ months or years”. fanfics writers write for themselves and their own enjoyment. they’re just kind enough to let you read their works for free. stop being rude and entitled to fanfic writers.