It’s not essential. But it’s quite common for kids to visit logopedist/speech therapist (and it’s also free service as a part of the health system, so easy to access) if they still can’t do it (or Ř, which is even harder) by the time they are 5 or 6 years old (a year before going to school).
We see kids as natural language learners but it takes them 4 or 5 years from the first words to the good pronunciation of R or Ř. So no need to get depressed if we can’t learn some sounds after several weeks (or months) of learning. I still struggle with welsh Ch, I say it correctly maybe half the time, I often revert to “normal” (velar) Ch or say it somewhere between. And also Dd if it is close to normal d.