Can Lumineers be removed? Well yes and no.
Yes they can be removed, but it's not quite as simple as it sounds. A great cosmetic dentist can remove them with almost no irritation to your natural enamel. It may take longer than it did to bond them on.
No in the sense that you really shouldn't go forward with any type of porcelain veneer treatment or Lumineers with the thought that you can remove them later or if you don't like them.
If you haven't had them yet, my advice is to get more certainty ahead of time from a conversation with your cosmetic dentist.
If you've had them done and aren't happy, then first sit down with your dentist and list what bothers you. If you don't get a concerned response or don't feel like the issue is really getting addressed, then you may want to get a second opinion from a cosmetic dentist.