Skill is required for all vehicles in War Thunder, no matter what other people might tell you. All war thunder gamemodes are combined arms, which is a core part of the game and advertised as such. The only exception is AAB, ARB and ASB, all of which are old gamemodes from when WT wasn’t a combined arms game. Although they did add AI units. Any air Sim player can tell you the horrors of mid map SPAA at all BR’s
Ground AB / RB / SB CAS influence
Generally CAS has a very mixed influence on the victory rate of ground realistic. It’s only at the very top tier that we see a large difference in impact of CAS compared to SPAA and other ground units. A lot of skill is required for CAS pilots to actually make a return on the invested Spawn Points, as most just revenge bomb the targets they know the location of from when they were in a light tank.
Generally a game will be easily lost if more than 3 players will go in a CAS vehicle, which is far more noticeable if you play nations that have famous CAS planes, like the USA at BR 5.7-6.7. Getting 11 kills in an AU-1 or another CAS-heavy plane is fine, but you can also make the same amount of kills with a Jumbo at the same BR and win the game by capturing zones.
If you want to win a game you need to play with tanks, Gaijin recently removed the zone capture ability of all airplanes except the harriers and yak-38 in order to facilitate that.
Being aware of the air threat and countering it with decent cover, the right movement patterns and skills to not be seen are also very important for your survival and an integral part of GAB/GRB/GSB.
Any decent arcade player can tell you that. And in realistic this is learned at a slower pace, but also very important. Don’t stay at the same place after killing an enemy. Always check how many SP the killed enemy will roughly have used if you want to stay at that spot. Don’t just look left and right, but also up. Etc. etc.
SPAA dominance
At the medium and especially at the upper middle BR’s of 7.3-8.7 we see extremely overpowered SPAA that are often 30 years younger than the tanks and planes often associated with these BR’s. Several of these SPAA are nuke printers, allowing any decent player to wipe an entire team in the first 5-7 minutes of the game, which is also an argument often used by CAS players to show that CAS isn’t the only powerful tool available in GRB.
Several SPAA can easily carry a match on their own. They just require more skill.
My experience
I also play CAS on occasion in GRB, mostly when I have other squad mates I’m assisting that might have less skill at the game and need assistance if they are cornered by several enemies. (And where I’m not concerned about winning the game)
CAS is also a very much needed tool to combat spawn campers or people that abuse overpowered positions on the map, often the only option to try and turn the game in your team’s favour.
At least, that’s my experience for BR’s 1.0-10.7. at top tier it’s far more toxic imo, and there both CAS and SPAA are really unbalanced both ways. Decompression and equal platforms for all nations are badly needed there.