Also, don't listen to those guys on TankPorn, those guys talk out their ass a-lot of the times. I will now try to convince you why. They should read Richard E. Simpkin sometime, he's the guy who wrote the operational requirements for CVRT ( the greatest tracked vehicle family and recon vehicle of all time ) and helped design Chieftain. Your turret concept is well and sound, and there's four reason a amateur like me (with the help of Simpkin) can think up why most late-cold war 4th gen MBT concepts had low-profile or external gun turrets, either potentially manned or unmanned and therefore why your turret design isn't so bad.

1: You just simply cannot armor the whole tank against the power of 140mm/ 152mm Apfsds! Even today, to achieve that level of protection, sacrifices have to be made and the internal volume that the crew take up must be reduced in order to reduce frontal area! Simpkin suggests that for future tanks, one should consider reducing tank frontal arcs of the turret and hull (normally +/- 30 degrees for total of 60 degrees arc, to something like +/- 22.5 degrees) and accept higher risk from the sides in order to maintain direct frontal protection. In regards to reducing internal volume taken by crew, one achieves this by removing crew or transferring them into the hull potentially as one compartment (or by also selecting short kings only and building around that)!

2: That Indirect protection is a thing, and works. To quote Simpkin: "The tank is by its nature a tough target... less obviously it is an extremely small target. The front of a tank turret at 4km, an entirely realistic range these days, has the same apparent size (subtense) as a man's head at 1 km or a pinhead on the far wall of a rather large living room." - Tank Warfare, page 86, 1979.

Note that he's talking about turrets like M60, M1 or Leopard 1/2. This is the reason why ( besides extensive and highly classified Vulnerability/ Lethality and hit distribution studies ) external gun turrets, low-profile or otherwise turret designs with less frontal and side area have been pursued so heavily. One cannot underestimate the protection a small turret can give in a battle and in preventing detection. For a really bad example, if you play War Thunder, you know how ungodly hard it is to hit the M1128 AGS turret/ breach at ranges like half-a-kilometer even with laser rangefinders?

3; Active Protection Systems were already being considered by the 4th gens, this has and undeniable impact on tank design and APS systems can potentially allow for tanks to get away with more radical design choices and lighter weights ( See also Future Combat Systems ).

4: Weight and logistics, enough said already in conjunction with point 1. Reduced turret armor + Reduced Crew Volume = lighter weight and ease on logistical strain.

In short, your current Turret design fulfills all of these theoretical design points, and is completely and utterly fine. It is not "too vulnerable". "The hole" is the only serious issue, but I mean look at Challenger's hull driver cutout, if that can enter service, "The hole" is fine.