Arda Guler is a talented player and he has high potential, but in Real Madrid, his competition is quite tough, Vini JR, Rodrygo, Bellingham, so he only becomes a reserve player. This is certainly a challenge and also pros and cons in his heart too.
It's hard to be a starter when your competition is still in their prime. I think Trent or even Robertson needs time to replace Clyne and Moreno. Both of them have injury issues that affect their game time too iirc. Unless the same thing happens to Madrid, Guler won't get regular minutes.
A youngster like Yamal is an exception. I guess Arda Guler can try to do the same. Waiting patiently and when given the chance, makes a big impact that will encourage the fans to make noise in a match. It does feel terrible when you don't know when that time is coming though.