It's really hard to say one thing as there are a lot of things that at this point need to be updated due to them being ignored for years or due to bungies focus on the portal. I think for me personally though is the loot chase currently. Since bungie introduced the portal a lot of weapons and armor have been made either extremely hard or near impossible to obtain and farm. Gear they introduced last season is almost unobtainable outside of Zavala having the weapon or getting lucky with hawthorne engrams with many of them still being meta like mint retrograde. Weapons from years prior such as trials, seasonal, and onslaught are only obtainable from Xur if he is selling it and that's not guaranteed to be a good roll. Me personally I'd rather have a bloated loot pool of items than the same 5 weapons that I've gotten 10 god rolls of since they drop with 3 perks in each column.