I would tread carefully before kicking out your managing agent. You need to address the reasons as to why things are not getting done by your managing agent, as otherwise the problems do not go away. They usually get worse as the new person takes time to get familiar with the place.
You really should have appointed representatives from the ownership (the management company) who then meet regularly with the managing agent to direct what needs to be done, update on issues arising, what the budget should be, what the budget should be spent on etc. Remember the managing agent is like your employee. If you paid your employee, but never met them, didn't tell them how much money they had to spend, didn't know what hours they were working, didn't set deadlines, didn't set priorities, well you can imagine your business would be run into the ground. Your apartment block is your business here. You (or collectively the owners) have employed an agent to run it. It needs to be run in a business-like fashion if things are to be done properly. You need to educate your fellow owners about this, or take responsibility yourself.
I was in an apartment block where we changed the managing agent thinking that would solve the 'problems' but it simply meant the problems transferred to a new agent who took years to even get up to speed.