The way I see it, fishing is somewhat unique content for two reasons. First, it is not schedule-agnostic: log progress can't be made whenever you want, and the schedule is determined by the game, not the player. This is fairly different from most of the other time-consuming achievements and such in the game, which can at least be worked on little by little whenever a player wishes. Second, even if you do everything right, you are not guaranteed the fish: this sets it apart from something like hunts, where even if a mark doesn't spawn for a long period of time, if you show up when it does spawn, you know for certain that you will get kill credit for it.
To be absolutely clear, I enjoy this about fishing and I'm glad it is like this. However, that also means its balance isn't really comparable to other content in the game: a 20 day average wait might be fine for hunts, but it is dramatically less so for fishing, especially with a fish that appears to be moderately uncommon even when it is available. I know quite a few people, myself included, that are going on 3-4 full windows with no catch.
Purse of Riches is unavailable for an average of 20 real-life days at a time. Assuming the average player spends 2/3 of their time at work, sleeping, eating, or otherwise doing anything that is not playing the game, that means most people only get one attempt every 2 months. This already feels bad, but it also averages multiple windows for a single catch, which makes it worse. For me, it crosses well over the line of healthy, fun friction into the territory of frustration and stress.
I've seen some people say that it's okay as long as it's just the one fish out of hundreds. The idea that one fish is widely-regarded as bad and upsets players for potentially months is fine because most people will only deal with it once is unsatisfying to me, which is why I'm so critical of this fish. To be specific about my perspective and the kind of player that I am: I intend to catch this fish multiples times regardless of what happens for data-collection purposes. I'm probably less emotionally invested in a first catch than most people. The availability of this fish is still rather disheartening for me. I understand that pushing variables and trying new things is fundamental in design, and that there is no precedent for a big fish being adjusted, but I do wish we could see some sort of response on this. I really, really love fishing in this game. I would like to love it even more!
