Part of the issue with a photographer’s self image is this:

The only people telling them about their work are their own clients. Most of which will say they were great. It gives a false sense of excellence over time.

Another part is… the average person has no idea what good vs bad photography is.

Presented with these two issues, a barely competent photographer can produce sub par work and his customers will love him or her for it. Do that for a few years, and they become jaded, and well… burnt out, and don’t seek to improve, since… why? Their customers love them.

It’s a vicious cycle I’ve seen for 30 years in this business.

This is a multi-part problem.

1. Suckiness is in the eye of the beholder. What you look at and say “sucks”, someone else will see the height of art.
2. When the ratio of providers to customers gets messed up (like it is now, when anybody who can afford a digital camera is suddenly a wedding photographer) – then we expect quality to drop … but in fact what is happening is that price expectations of the customers are dropping – so the market right now is (often) price-driven, not quality driven.
3. Most people do not appreciate good photography. They only have their own photos to compare it against. If you can do at least as well as they can, they you must be good, right?
4. Wedding photography is a unique bird – most customers are one-time; the photographer is often the last to be hired.

I think all you can do is listen to people you trust to judge your own work, and keep trying to improve. Eventually, the photographers who compete on price will be driven out of the business, and the customer who shopped on price will get frustrated with inferior results, and seek higher quality providers.