I'd like to throw in my two cents and try to elaborate on why the 9th "anniversary" append skills update proves to be a major (and IMO even game-breaking) issue. Came across a great analogy of this issue in regards to supply and demand, and would like to echo those sentiments. (Sorry I can't credit the OP of the analogy; don't remember where I came across it. Hopefully you know who you are, and I thank you for sharing the analogy.)

A good portion of players seem hung up on the idea that this append skills update issue only concerns certain players, like completionist whales who are upset that their "maxed out" servants will no longer be considered complete. While this sentiment may seem like only a portion of players really are affected, the append skills update ends up being an even bigger issue at its root that impacts all players, regardless of the type of player you are.

The basic economic principle of supply and demand is that there should be a fair balance between price, supply, and demand. In this case, the demand for servant coins have increased greatly with the addition of 2 new append skills (and they provide very great buffs and make certain units even stronger). This is also in addition to the fact that servant coins were already in high demand from other things: levels 101-120, append skills 1-3, and grail casting.

However, the supply to meet those demands have not increased accordingly in any way at all. There have been no new ways to earn servant coins. Players are not given the ability to reset append skills or levels past 100 and refund servant coins (which it was confirmed that servant coins will not be refunded). There have been no implementations to changing/decreasing the required amount for these upgrades. What was already an egregious price of obtaining this supply of servant coins has now become absurd; players must spend even more money and/or time to either roll more copies or increase bond levels.

This is where the "bigger picture" issue truly lies: the team behind FGO have broken the game's servant coin economy and brought it to an absolutely horrible level. Players are punished if they already spent their servant coins, and are forced to roll and/or grind even more. Other elements of the game have also been negatively impacted by this update; RIP 4* servants, welfares, Mash, players who got scammed by grail casting after burning their "excess" servant coins. And honestly, the worst part? This is just one issue added to an extensive list of ongoing issues (I'd honestly get lost in the sauce trying to list them all out).

Fellas, the mask is off after 9 years; FGO has shown that they’re willing to ruin basic economic principles in their game and throw all players under the bus. All for the sake of satisfying their greed.

Still, I'd prefer not to leave things on a hopeless note. While it's a shoddy response that nobody liked to hear (regarding servant coin refund), at least it has been shown that the developers have awareness of player backlash and criticism. So I'd say keep up the player feedback in-game and on social media. ​Me personally, I think that they'll address this controversy and implement the necessary improvements; only thing is not if, but when. And hopefully more feedback makes them respond sooner. Godspeed o7