Ancient
Just wondering how can I feel the bottleneck, as I'm not seeing issues with latest games and Valve Index / Half Life (I guess the GPU is quite unused is my understanding? - although I'm not seeing the CPU fully loaded and the GPU is optimal used).
Yea I mean it's 10-11 years old, 1st gen Core architecure.
Well first of all you don't have to feel it, but upgrading your CPU would increase your framerates further / smoothen it out and make the gaming more pleasant. (*You can check the GPU usage with MSI Afterburner and the included Riva tool has an on screen display which lets you check the usage while in game, or you simply put the tool on second screen and check the GPU usage part. If it is less than 99% either the game doesn't need a strong GPU, or your CPU is not feeding the GPU enough data to let it stretch its legs. But you can check CPU usage there too, and that's another way to see if your system is being limited or overburdened.)
*Edit: I noticed you didn't ask "how", but I can assure you, this CPU is most certainly too weak for a 2080 Ti. I have a 1080 Ti and it was bottlenecked by a 3960X at 4.5 GHz in BF5, thats a lot stronger CPU than yours and the 1080 Ti is obviously slower than its successor. I then bought a new CPU and got a lot more performance, usage went from 60%-70% to 99%. This was in 1440p Ultra, no 1080p nonsense.
The problem is if they put the case side on there will be nowhere for the air to go execpt out the one rear vent. Very inefficient airflow.
That's not inefficient my friend. Excess air, as in positive air pressure, will always be pushed out. This means, the hot air will leave the case quickly. I have a positive air pressure case myself, not only does it work very good in keeping temps in check, it also decreases dust build up. Understand air as "mass", if the case is full, it will be forced out, the one outgoing fan he has should be sufficient.