Take EXACTLY the same design, layout, and feel the season 2-4 client had IN EVERY SINGLE ASPECT, with the addition of Practice Mode + In-Client Item Shop/Item Creation Builds.
The first impressions and continual use of the new client has the same feeling of EVERYTHING IS DONE WRONG AND POORLY! This is the complete opposite of my impressions of the client back in season 1 where I sang praises constantly of how great the game client was, and to this day I still do because most of the new stuff implemented ended up being a downgrade. New things should be an upgrade (RIP good NA UI for MapleStory, reverted after a patch, I loved that new UI and still don't know why Nexon reverted it; just to show it is not new things I don't like, it is bad things I don't like).
New client just seems like, and still is like that, of a really shitty early incomplete concept of an extremely early test alpha build of a concept for a client that is no where near what the finished product should be. The finished product should be something exactly like the seasons 2-4 client, which til this day I have still not seen a game client come anywhere near the master piece of that client in its design, layout, feel, ease of access and navigation, you name it; so the client needs to reverted to something that is tried and true of being vastly superior.
I would give specifics of what to fix, but everything in the new client is bad, and I literally mean everything. Where as the seasons 2-4 client is perfection, and I am saying perfection because there is yet to be something better for a game client, minus the improved dev tech for Riot, practice mode, and item shop.