I beg the pardon of you all here but you seem to forget a couple of things about "tank development", the vehicle at hand and how generally military institutions tend to operate.
a. We are talking about a specific situation which in recent history has happened very few times. That is IFV auto-canons penetrating the sides of an MBT turret.
-These cases have been proven in ODS and Ukraine recently.
-The said cases had happened due to both tactical errors, material inferiority of the MBT's and generally a very poor state of the MBT unit who got attacked.
-The case of ODS (73 Easting) while much talked about, was a situation that happened because the Iraqis were overrun by the US tactical group. The fact that the Iraqis in static dug-ins were in one case taken out by 25mm (some say from the rear of the Turret at point blank range) is basically an outlier and is no basis for concern (The T-72's were being smacked by US heavy armor and FCS capability).
-In the case of the 2nd Separate TB of Ukraine that was ambushed by LNR (cough Russians cough) BMP's and lost 3 T64BV to penetrating shots, is also something that is an outlier. And relies on a bad tactical decision from the CO's. As such the fact that both sides came that close, is an outlier. As BMP's would rarely venture that close. Before you bring up Thunder Runs of 2003 fame, the level of luck and speed and organization versus the lack of all those in Ukraine, should be pressed forward.
b. We are talking about a vehicle which by nature is going to be engaged in a unit. A unit that will cover angles, operate with other supporting vehicles. If your cohesion and inter-operation as a unit breaks down at that point, then again, there's no level or armor that would help you.
c. The "it shouldn't happen" is exactly why you have a doctrine which lays out objectives, TTP's and thresholds to evaluate those. Both in capability and efficiency.
If your military unit can't establish its goals (which are mainly military translations of political calculus), pursue them within the threshold of violence and losses then a review is in order. But those doctrinal lines cannot simply be to make everything "unkillable". Because cost for starters. Furthermore, a case of "making" things "unkillable" in first glance will always have an escalation. This escalation is only possible if the conflict at hand isn't terminated. In the case of Israel, that conflict is unsolvable. But in the case of Russia or the US, the conflicts recently have all been solved (on their "hot" phase) rather quickly.
d. The vehicle we are talking about is satisfactory when taking into account how a military unit should operate. Furthermore its layout makes it easier to both up-armor if need be, but also protect as it is.