People who engage in radio frequency will never lose their jobs, because communication systems are constantly developing, such as 2G\3G\4G of mobile phones. Every time you upgrade, the frequency will increase, because the higher the frequency of electromagnetic waves, the faster the data will be transmitted and the more data will be transmitted.
As the frequency changes, the antenna and filter will also change. Because antennas and filters are designed according to frequency and wavelength, different frequencies cannot be used universally.
Every time the communication system is upgraded, operators have to save a lot of money to build communication base stations, that is, those antennas. Look how rich Huawei is. You will know what the future of RF is like.
Of course, RF is not just about designing mobile phone antennas. It can be said that all electronic devices that transmit data through wireless technology have antennas and filters, such as wireless mouse, wifi, Bluetooth and so on. People can't meet the existing needs, for example, people always complain about poor signal, which is largely due to poor antenna design, insufficient coverage and poor gain, so we need to design better RF devices.
You should have studied electromagnetic fields and electromagnetic waves, and you should know whether those things are difficult or not.