Is doing Dua after Salah an innovation/bidah?

So we know it's authentically narrated that the Prophet sallallahu alayhi wa sallam made dua in congregation with the companions at certain times. For example, at the time when they were making dua for rain, Salatul Istisqa for the time for the fear prayer as well. Now the issue often comes after Salah. If you want to make dua as an individual, no issue with that. Nobody says there's any problems with that. In fact, it's a good time to make dua because you've just prayed to Allah, asking Allah to accept your Salah and so on. Some have an issue when it's in congregation. Now, when it's in congregation, even those that mention this particular issue, they say as long as it's not done to mean that it's every single time after the Salah, so it's considered to be part of the Salah in and of itself, meaning that if you were to miss it, you would be sinful. As long as it's not considered like that, then it will be fine. So for example, Imam Ahmad has this view famously and also even many of the Saudi scholars such as Shaykh Ibn Uthaymeen had the same view based on those conditions.