Zuranthium
Casting your favorite spell
Semi real creatures and objects has been Illusion magic for 40 years? Semi illusory creatures and objects were created by illusionists back in AD&D
That's not how it should be. That's literally not the definition of an illusion.
A master illusion caster is Iris from the Xanth series. Anything else is something different. A half-illusionist, half-summoner (but actually not even that, since you can still use all the other schools of magic as a 5E caster).
The entire design of casting subclasses in 5E is trash, especially for Wizards. A much better design is school specialization blocking off another school of magic, to give a bonus to the chosen school. It should also be possible to block off as many schools as you want, gaining a bonus each time. Thus:
A full Illusionist can use only that school, and should gain 7 benefits to Illusion magic in return for losing 7 other schools. Or if you want to be "semi real illusionist" that would be an Illusionist with 2 or 3 less tiers of specialization into that school, combined with Summoning Magic at tier 2 or 3.