There’s no fixed number for how many is too many. Instead, consider the following:
Never install anything you don’t need.
Install quality plugins - poorly written plugins can slow your site down and even crash it
Your webhost - budget or shared hosting can handle less than cloud hosting dedicated servers (HostGator and Bluehost have good hosting options).
Site load times - 40% of site visitors abandon sites that take more than 3 seconds to load.