Can't add anymore fields / blocks to Matrix Field
There's nothing in Craft limiting the amount of Matrix Blocks and fields you can add, it's purely environmental.

The most common values to increase are max_input_vars, post_max_size and memory_limit, so you'd need to bump one or more of those to higher values to be able to add more.

If you're running things like Suhosin or mod_security, they provide their own additional settings that sit on top of php.ini settings that you might need to adjust as well.