Mirage 2000s are multirole aircraft - they are primarily used in the IAF as tactical strike platform but can engage in air combat as well.
MiG-29s on the other hand are developed as pure air superiority fighters. They are meant to provide air cover for up to 100 km behind enemy lines. Remember, in the Soviet military doctrine the frontal aviation (which includes tactical fighters, ground attack aircraft, and utility) was seen as a mere extension of the ground forces.
However, IAF doctrine is changing. Instead of many different types of aircraft with specific roles (like MiG-27s for just ground attack and MiG-29s for just air superiority), the IAF wants fewer types with mutirole capabilities (like the MMRCAs).
For this reason, IAF will not induct any more MiG-29s. Although the newer MiG-29SMTs/UPGs and MiG-29K have ground-attack capability, they are just air-to-air fighters first and foremost.