I don't mind the hats, they're quite amusing and add some harmless variety, but the constant influx of new weapons and usable items is a bit intimidating now.
I've been playing since the beginning, and can't help but feel that they're cluttering the game up with a lot of useless crap (dalakohs bar anyone?), whilst rendering some of the original weapons obsolete (Equalizer has replaced soldier's spade, medic's regular saw is pretty pointless compared to ubersaw, etc). Besides that, some of the new weapons just make the gameplay 'confused' - a sniper rifle that can't headshot anyone? Milk that when thrown at the enemy will allow you to regain health when shooting them?
It's all starting to make the game less straightforward and somewhat off-putting to play, especially if you only play the game occasionally and don't know about all the new stuff they've added since you've last played... you'll come away confused and frustrated, and perhaps even not bother playing it again. In my opinion they now need to clean the game up before even considering adding anything else - balance the new stuff out, update obsolete stuff to make it worthwhile to use again, and remove pointless junk.
Oh and while I'm at it, don't care that they've added microtransactions - if some people want to get an item without waiting, then fair enough. However, adding random item crates that drop for all players, yet you can't do anything with them unless you pay £1.99 for a key to open them... I think that's going just a bit too far.