The emphasis in Tennyson's poem, "Ulysses," is not on the failings of the people of Ithaca, although they are mentioned. Most of what is revealed about them is contained in lines four and five: they are "savage" and "hoard, and sleep, and feed, and know not me."
The people of Ithaca, then, in the speaker's view, are violent, uneducated, obsessively hoard food, etc., do nothing but eat and sleep, and don't understand Ulysses. Presumably, they don't know what they have in the hero of The Odyssey. Presumably, they don't honor and listen to him as they should.
The people are also "rugged," as mentioned in line 37. It will take a calm, mild-mannered, diplomatic man like Telemachus to "Subdue them to the useful and the good." Ulysses is an adventurer and a warrior, not a diplomatic leader, according to the poem.
Tennyson presents Ulysses as somewhat of an artist. His adventures are artistic. His mindset is not that of a diplomat. He longs to be off on an adventure, and he wants to leave the leadership of his people to someone else.