Seems a bit wasteful to buy a new heater when it still actually is
mechanically sound and heats fine all for the fact that it has an
obviously large amount of sediment and crap in it

Trying to clean it out is my first option


I had a similar problem

You really need to call a professional, depending on your heater they
may or may not be able to remove the heating element(s) and get large
hole access to the tank that way and give it a good cleanout