Well be glad that this partnership happened because codeveloping is what's giving way to Toyota building a new A100 Supra by themselves only. Realize that there would be no way that the project would be green-lit if it wasn't for BMW joining in the partnership.
It's a car with quite a few flaws I must say, but the fact that it's here, makes me so happy.
The problem here is that the car punches weigh below the weight classes of prior Supras, and even with the partnership this did not have to be the case, especially with a scalable architecture. There is a healthy middle ground between "100% in house to make a top tier sports car" and "using all BMW parts to make a mid tier sports car."
If we go a step further, why co-develop this incredible sports car architecture with another company on a single model just to abandon it for another new platform 6 years later? Why not use this scalable architecture to make what they wanted in the first place? This just brings them back to same spot they were in before the partnership, one without a platform suitable for this caliber of car thus making the A100 incredibly expensive to develop.
Sports cars are expensive to develop and it is clear why a partnership was necessary, but this partnership should have been used to create a lasting, scalable platform to use across multiple models, such as the Supra, 86, and RC.
For clarity: There is a misnomer that the BMW complaint is solely a 'partnership = bad' complaint, when it is much deeper. An argument can be made that Supra is comprised of more than just RWD 2 door coupe and also requires the additional qualities of a GT/sports car, top tier competitor, and a car that showcases new Toyota development. These qualities are objective qualities that the A90 lacks and which I believe had the potential to be achieved even with this partnership.
This would be done by using the same car, same partnership, same suspension, same platform architecture, same transmission, same Magna Steyr assembly line, but 5% larger (which would make it 911/AMG GT/NSX/LFA size) and with a performance tuned V35a mounted behind the front axle. This would make an excellent car that competes in the same market segment as the previous Supras, a car that showcases new Toyota development, and all while utilizing the great partnership that makes the MKV so great. I feel like this would have been a car way less controversial while still being a great driver's car as it is today. Of course this would increase price, but even if it goes up ~$20k-$30k, it would still be much cheaper than it's competitors.