I agree with you. It's very possible to match into competitive specialties as a D.O. I should have been more specific and used "very competitive" or "hyper-competitive" like ortho, derm, plastics, ENT, etc. I really do believe it is possible to match anything as a D.O. I've heard of DOs matching into every single specialty there is, including the ones I just mentioned.
But from what I have seen, being a D.O. makes it much more difficult. There is a strong bias against DOs, particularly in these specialties. They are obviously better off than IMGs and FMGs, but they would still face more of an uphill battle to match into the very competitive specialties than an American MD would.
Program directors, attendings, and residents (within ACGME residencies, which make up the majority of residencies) have explicitly stated that DOs are generally not even considered. There are too many applicants to sift through for these hyper-competitive specialties, and DO schools are generally considered to have inferior (their words, not mine) clinical training. The only DOs that do get considered usually have extremely, extremely high board scores, a very high number of publications, and/or have extremely good connections. You typically have to have at least one if not more of these characteristics to have a good chance at matching. This is just something that I have observed. In the short term, it appears the merger will make it even harder for DOs to match into these specialties because previously DO only programs will be open to MD applicants. Ideally, these programs will maintain favor toward DOs, because they should want to see their own prosper, but I am not very confident of that. You can read more about this in the merger thread in the DO forum.
Trust me, I am not one to make baseless generalizations. I truly believe in "it only takes one". You just need one school, one program, one whatever to give you a chance, and you will have the opportunity to fulfill your dreams. But at the same time, I really do believe in maximizing your chances every step of the way.