Some of default aircraft are good.
Not study level, but I can say they mid to high in depth.
I really like flying H225, C404, C408, A400M, H125, CH-47D, Skycrane, A330 and Beluga. There are few more, but doesn’t come on my mind right now. I am flying them and will in future.
They are not in depth like A2A, or PMDG but for price you bought the sim, they are quite good.
But I also, agree that they will need more to focus to core sim. Just for one reason, make good foundation for addons and make good environment.
And about aircraft, everyone have different wishes. Someone want to fly comercials, other want GA, another one military, so particular person will buy or download free aircraft which suits the most he’s wishes.
I am not very demanding simmer, so for me iniBuilds level is good, but someone else is not satisfied. There are people satisfied with Captain Sim.