Biggest issues I've encountered over the past 10 years (and getting worse in the past 3-4) are as follows:
1. The game is grindy asf.
2. The default client really sucks.
3. The combat system is obtuse as hell and I'll never be competitive unless I treat the game as a second job (probably not even then).
4. Trading has gotten much harder over the years for casual players. I remember the days when you could buy decent stuff with some blueberries and flotsam, and I am not paying real-life money just for gear in a game I'll quit in a few months anyway.
5. The FEPs on foods have gotten so complex over the years that I can't keep up with what combinations are "optimal", or with what ingredients will give what results.
As far as solutions go, I don't really know what to do about 1 and 4, but there are a few long-term ones for 2, 3, and 5 that should be implemented.
2. The devs should add more QOL features to the default client, like different camera modes and the grid view. I stopped playing regularly because it was too much of a pain to do ordinary tasks once Amber stopped being updated.
3. My preference would be for the devs to make pvp into a rock-paper-scissors type game, where there is a stat cap on combat skills and players can win by taking advantage of their enemies' weaknesses.
Ranged players should counter two-handed players, one-handed w/shield counter ranged, and two-handed counters players with shields, or something similar. I think that this would make it so that the most important things in combat aren't stats, but gear quality and strategy, since any player can potentially be beaten by someone (or some group) who has brought the right gear to a fight. This is a lot more intuitive than Haven's system, and I think it would also give combat a lower barrier for entry since you wouldn't have to grind stats endlessly to stay competitive.
5. Make it so that FEPs in a food are more predictable. As it is right now, depending on what kind of wood I use to smoke something and what ingredients/seasonings I use, there are thousands of combinations. For instance, red onions seem to give INT when put into pirozkis, but give STR for steak and tubers (and even this is not so simple, because pirozkis don't give INT if you make them with both red onions and bay boletes). Why? It's so damn complicated to try and min-max recipes when each ingredient gives a different, completely arbitrary bonus depending on what food I use it in. Ingredients should always give the exact type of FEP that the base item gives, e.g. Bay Boletes give DEX and CHA if eaten raw, so when added to a food, they should only give +1 or +2 DEX and CHA and never anything else.
TL;DR: The game has become an even bigger headache than it was in Legacy and needs an overhaul, especially in client QoL, combat, and FEP bonuses.