I find complaints like this one really annoying for three reasons:
1. They indicate someone who is more interested in complaining than in taking a good look at the information that is freely available on these boards.
2. They indicate someone who doesn't want to think. If I see a pet recommended in a guide that I don't have, it is easy and interesting to look up an alternative pet with the same or similar abilities that can be subbed in. You can do that right here on this very website: http://www.warcraftpets.com/abilities/unique/
3. They fail to appreciate the many, many folks on these boards who have put tremendous effort into posting thoughtful and comprehensive guides, sharing links and tips, and making sure everyone knows about websites offering assistance ranging from full guides to video demonstrations, all using easily attainable pets. Some of these posters are kind enough to share their own site and blog content here rather than link it. But hey, let's complain instead.
Honestly, if your first reaction to seeing that a specific pet type may be useful is, "ffs, another to level to 25" then I'd suggest you engage in pet battles at a more casual level.
As to another poster's suggestion that Blizzard "slow down" on making new pets available: Are you kidding? New pets help fuel interest in both pet collecting and pet battles. Suggesting that this stop makes about as much sense as suggesting that Blizzard stop releasing expansions because the new content costs money and the changes might overwhelm new players =P.
Blizzard's responsibility and challenge is to make a wide variety of content available to players who have different levels of interest. Some people will never do Heroic raiding. Some people will never do competitive PvP. Some people will never collect every pet, or win every pet battle tournament. That's fine, so long as there is fun and accessible PvE/PvP/pet battle content available at all levels. Blizzard has done a pretty good job with that nearly-impossible task.