You should consider that by the time you finish your PhD (in 3-6 years), the demand for experts in ML/DL will have gone down significantly - either because the

You should consider that by the time you finish your PhD (in 3-6 years), the demand for experts in ML/DL will have gone down significantly - either because the next AI Winter has finally arrived or there is simply an oversupply of experts in this area since currently the majority of CS students wants to work in AI/ML/DL. In contrast, there are a number of open PhD student positions in systems here in Germany for which it is extremely difficult to find appropriate candidates. The few students interested in systems topics receive excellent offers from they industry and leave academia after graduating with a master (and sometimes even bachelor) degree.