Yeah, just seem very passive from their side so far, considering numbers and hundreds and hundreds of planes.Aye, which reduces the risk to their modern arsenal. Yet, there's been valid questions about how effective their supposed superior jets actually are.
Russia has been very hesitant to commit them, even at the start of the war, so you'd ask yourself why when they should make the difference.
Maybe, they know they are irreplaceable (jets and pilots), and they aren't as superior as they may want us to believe they are - e.g. they're vulnerable.
Like take Bakhmut for example, months of bloody combat and i don't remember ever reading that Russians used airforce in any large numbers to try to soften Ukrainian defense. Like remember Aleppo few years ago (or Americans bombing ISIL capital of Raqqa), it was opposite