Normally you are right, but there are exceptions. Here is one: I currently have an Antec C8 double chamber glass case. Before that i used traditional mesh cases (Fractal Design Pop Air, Endorfy ARX 700 Air Edition). Those were all not audible in idle. I use fan curves and have a semi-passive oriented Rig (e.g. an oversized PSU, so I can run it in passive mode most of the time). So mesh was all good and silent. BUT: I also have a 4090 running in semipassive mode that slowly heats up when watching YT or similar and sometimes ramps up the fans to cool down to passive mode. GPU fans are running a few minutes and they are not loud but the ramp up itself is very audible (in complete silence). This was with the mesh cases. So i gave the C8 ARGB a try because of it's good GPU temps. The C8 has two gigantic 160mm PWM fans in the bottom. Those are apparently dedicated to the GPU and work very good, see the GPU results without side intakes (just the GPU fans and one outtake) at Gamers Nexus. So, top of the class temps with 3 fans only (albeit, 2 of them 160mm). Now imagine this with 3-6 additional case fans (which heal the somewhat mediocre CPU temps in default configuration) and you have a great case.
To conclude: My 4090 is now a lot cooler than before in idle and light loads. It almost never spins up and the sum of the experience is that the glass case is even more silent then the mesh cases. Just for comparsion: The ARX 700 I had before had 5x Stratus 140 PWM and an additional 3x120 in the AIO 360 configured as outtake. The Airflow was really good in this, so was the noise (confirmed in various reviews) and the Antec C8 is still less audible because of my 4090 and said 2x160mm case fans directed at it. The GPU was the one thing in my rig that kept me from a good silent light load experience - and now this is under control too. As a sidenote: I also added 3x140mm fans as side intakes in the C8 to create some air around CPU, VRM and GPU backplate (as my 4090 is almost 4 slots and 353mm, it eats up most of that bottom air). Even if the C8 manual does not list 140mm for side intakes, they fit with some light well-minded force
. So this may be also part of the solution.