The number one reason why Somalis think they suck is because of self-esteem issues. Somalis have tremendous egos that are also incredibly fragile. We say we're better than everyone, but secretly harbour feelings that we're not. Somalis often think that a non-Somali can do a job better than a Somali (don't believe me? Go to Somalia/Somaliland/Puntland/Djibouti - I've been to all of them and the problem is the same; the locals will fawn over any foreigner with light skin, while educated Somalis who actually have a vested interest in seeing their people succeed are often moved to the sidelines).
Conversely, contrary to what some people say, we do have several reasons to be proud:
1. Somali civilization stretches back over 5000 years when considering archeological sites such as Las Gaal (no tribalism - we were all proto-Somalis then). There are numerous such sites littered all over Greater Somalia with tombs and ruins. There is also evidence of a written language from around that time, which was replaced by the wadaad script circa 7th century. That would mean that the ancient Somali written system would be tied with Ancient Egyptian as the second oldest written language on Earth after Sumerian.
2. The ancestors of the Somali nation accepted Islam peacefully before the Hegira to Medina. We have the oldest masjid on the African continent. Don't believe me? The masjid in Zeila has two qiblas - one facing Jerusalem and one Mecca. The one facing Mecca was added after Surah Baqrah verse 144 was revealed to the Prophet (PBUH), circa 623 CE. That is decades, if not a century, before the before the majority of Arabs converted and nearly 1000 years before south Asians - groups who both like to pretend that they have a longer/deeper association with Islam than we do.
3. The modern dromedary was domesticated by around 3000 years ago, and today, Somalis have more camels than anyone else on the planet. If you've been to the fatherland, you will know that it can be a very tough land - life was made much easier across all nations with deserts because of camels.
4. The land of Punt is postulated to have been based in Somalia. This is based on not only historical evidence in the form of Egyptian records (anecdote of the Voyage of the Sailor, Pepi's expedition in 2200BC, Hatchesput's expedition to Punt around 1470 BC), but also on flora and fauna (animals sent to Egypt as gifts, Egypt sourcing it's frankincense from Punt.
5. The rise of powerful Somali city-states afterwards (again, every region had clout and cities - no tribalism). They dominated trade in the Indian Ocean and Red Sea, preventing Chinese and Indian traders from accessing the Mediterranean. Somali traders would buy Indian spices which they would sell to Rome, so much so that the Romans called Somalia "Reggio Aromatica" as they thought that it was the source of all incense (which was fairly accurate) and spices (which wasn't - Somalis just dominated Asian traders and sold it for profit to Romans).
6. The Adal and Ajuraan Sultantes - medieval mega powers that rose to prominence in the north and south. Adal was using firearms in the 15th century - far, far earlier than the majority of Europeans, while Ajuraan was feared by even the mighty Portuguese Empire, the most powerful state in Europe. The two fought several wars over colonies in Mozambique and control of the Indian ocean. The Portuguese were scared of attacking Xamar during the wars as there was a legend in Europe that Xamar's skies were protected by griffins. The colonies in Mozambique are were Somali bantu originated from. To this day, a province in Mozambique is named "Sofala" - literally "Go dig".
7. It took the British, French, and the Italians to colonize the Somalis, and even then, they put up the longest anti-colonial wars in African history and Europeans were never truly successful in controlling all of Greater Somalia at the same time. Find one other nation on Earth that were colonized by three powers and still fought as the Somalis did.
8. As mentioned above, Somali women are unmatched in beauty. No one even compares. No need to elaborate further.
9. And, last but not least, these other guys may be putting people on the moon, but they still don't know how to wash their ass when they take a dump.
Does being Somali have it's challenges at times? Yes. Would I rather be something else? Hell no. God created me out of the best of the best and I have no self-esteem issues. It's up to us to claim our rightful place in the pages of history. Or, you can just sit there and be part of the problem by complaining about how much Somalis suck whilst having no discernible talents or meaningful contributions to improving our station.