I think that when most people talk about reaching a native level, they usually mean achieving an accent that sounds indistinguishable from a native speaker. This is when a native listener wouldn't be able to tell you're not a native based solely on your voice. The issue, however, is that a significant number of people never reach this level, no matter how they've been learning the language. In my native language, portuguese, I can think of several public figures who have lived in Brazil for decades. Some of them may even have more exposure to portuguese than to their original languages by now, yet as soon as they speak, it's clear they aren't native speakers. Interestingly, two examples that come to mind are individuals whose native languages are quite close to portuguese, like spanish and french (Paola Carosella, Érick Jacquin). They've been in Brazil most of their lives, they literally have more time with portuguese than I as a native do since they are way older than me, but they still have notably strong accents that will certainly never go away. So, even if you're willing to invest the time to sound native, it's very possible you may never completely achieve that level. I really think that for some people, reason, it's literally impossible. I'm really inclined to think that "sounding native" for adults learning a second language is almost an urban legend. It may be anecdotal, but I've never met or seen anyone who learned portuguese past their teens and didn't have a clearly noticeable foreign accent, no matter how good their portuguese was. People really underestimates how rare this is and is definitely not only a matter of putting the time and effort.