not illegal. morally a grey area, perhaps, but the software and the devices it runs on are 100% legit. you’re streaming from sites hosting content that isn’t particularly legal, but via VPNs/proxies that constantly change to circumvent ISPs blocking the host IPs, and in the EU nobody has ever been prosecuted for streaming (as long as you don’t download content, you’re not doing anything outside of the law basically).
i find that the quality of both streamed films/TV and live TV feeds can be variable, but i’ve never had trouble finding high quality amongst the dozens of streams of each particular thing i’ve wanted to watch.
i have an android TV box, plus kodi running on two nexus tablets and my nexus 5 phone too.
i’ve never had a paid TV sub from any provider, nor would i ever get one- if Kodi didn’t exist, I just wouldn’t watch stuff unless it came on freeview channels. with that in mind, i’ve made my peace with my own streaming activity!