How is a hardcore, iron man, I quit, buried alive, boiler room brawl, casket, inferno, last man standing, the chamber, bra and panties or a tables match blocked from happening because of blood? Neither match requires it.
A couple of these gimmicks are dead because they are quite frankly, stupid. And even Vince gets that. It's not the PG rating, it's that they serve no purpose in today's media/wrestling society.
The bra and panties match? stupid (if you want this, there are plenty of fetish promotions or down right porn for people to watch online). Boiler room brawl: Stupid.
The inferno match is needlessly complicated and hard to set up and down right dangerous. Buried Alive is also a stupidly complicated gimmick to pull off and the casket thing is quite silly.
Then there are gimmicks that are just not brought back because WWE does not work with long running feuds that would logically culminate in those types of matches, like the last man standing match, Elimination Chamber or the iron man match. Tables matches happen yearly at TLC so it shouldn't even be up for debate. We know we get one each year.
A lot of these gimmicks are easily worked under the PG banner so it is not even an issue of a ratings system. They are just not used because WWE does not structure its product to need those types of matches.