Explained by someone that doesn't know the technical side super well.

1: It's a new protocol for displaying. The main difference from X11, as I understand it, is a simplification of the stack. Eliminating the need for a display server, or merging the display server and compositor.

2: Some things impossible (or difficult) with X11 are much better supported in Wayland. Their not necessarily available, as the Wayland protocol is quite generic and needs additional protocols for further negotiation. Examples are fractional scaling & multiple displays with differing refresh rates.

Security is also improved. X11 did not make some security considerations (as it is quite old, maybe justifiably so). In X11 it's possible for any application to "look" at the entire display. In Wayland they receive a specific section that they can draw into and use. (This has the side-effect of complicating stuff like redshifting the screen at night, but in my experience that has fully caught up).

3: If you're interested, are in desktop application development (but I have no experience in that regard) or have a specific need for Wayland.

4: I think X won't die for a long long time if "ever". I'm not super familiar with desktop app development, but I don't think it requires more work to keep supporting X.

On the other hand, most of the complaints about Wayland I've heard were ultimately about support. At some point, when you're a normal user, the distro maintainer should be able to decide to move to Wayland without you noticing, apart from the blurriness being gone with fractional scaling.