I really get that fixing things to properly work and still be able to use the seasonal theme. However from my point of view as a player and developer, I would simply disable the theme and enable a working one that does not effect directly leaderboard outcomes (e.g. double bounties / goblins).
You can’t expect them to fix it soon because as we already heard, there is only one (!!!) active developer working on a game with this scale. Plus, we have 2020 and corona, meaning workflow / time is already less then usual.
Beside the broken seasonal theme, there are so many small game decisions that help abusers and/or botters and do not get fixed by years. E.g. allowing people to join completed bounty runs and loot the caches. That helps those abusers even more and no normal person would loose anything with this mechanic just disabled.
So be realistic and try to set your own goals elsewhere. For example, try to compete with your friends only for your own personal leaderboard.