>>> airlines will no longer be bound by the compensation scheme for delays
Some will, some won't.
The compensation rules apply to all airlines based in the EU and to any airlines flying to or from an airport within the EU. So flights operated by Ryanair (based in Ireland) will always be covered, as will flights to and from the UK to any other EU country.
However long-haul flights originating or terminating within the UK will no longer be covered by the rules (unless, unusually, they're operated by an airline based within the EU) or flights to and from Israel, Turkey, Morocco, etc (again, unless they're operated by EU-based carriers).