A commenter correctly points out that the mithril coat worn secretly by Frodo is actually incredibly scarce and valuable - more than Frodo himself realises. (It came from the hoard of Smaug in The Hobbit).
As to the fellowship, I think an important point in considering the geopolitical situation of Third-Age Middle Earth is that the elves, after previous catastrophes, are in a kind of Vietnam Syndrome. They do not believe that any good can come of military action. The Fellowship includes nobody from Rivendell. Aragon was a ward of Elrond but is engaging in the operation as part of his project of uniting the Northern and Southern kingdoms of Men. Legolas is a visitor from Mirkwood. Elrond explicitly considers and rejects the idea of sending elvish warriors.
Rivendell is not a city-state or city, but a house - "The last homely house West of the mountains", as it is described in The Hobbit. It is something like a medieval manor house, inhabited by the Lord's extended family and a few guests and retainers. It is not adequate as a base for military operations.
As for importing supplies from Lothlórien, as suggested by ekr, that is absurd. Not only was there no Fed-ex, long journeys were extremely rare and dangerous. Elrond's wife Celebrían (Galadriel's daughter) was captured by Orcs on a journey from Rivendell to Lórien, and the wilderness only became more dangerous since. There is no mention of merchants in LOTR (the gathering of supplies to Isengard is the only trade I can think of), and the idea that the roads will be used by "messengers of the King, not bandits..." is a prediction made by Frodo after the fall of Mordor, in contrast to the past.
Possibly ekr was confused by the film, where Elrond and Arwen apparently teleport around Middle-Earth at random, and a mysterious Elvish army arrives from nowhere at Helm's Deep. This was due to the filmmakers writing and rewriting the story, and having to use already-filmed scenes after changing their minds about the plot.
The only plot difficulty I saw along the lines of ekr's objections was the low profile of the eagles. In both The Hobbit and The Lord of the Rings, the eagles appear as Deus ex Machina at the end to save the day: first in the Battle of the Five Armies, and then to rescue Frodo and Sam after the fall of Barad-dûr. In both cases it appears that they could have done a lot more good by getting involved earlier.
Even this problem I am no longer too worried by. Just because there is no air-to-air combat in Tolkien, one should not assume that air superiority is not a consideration. For most of the period of The Hobbit, there is a dragon in the Lonely Mountain, and the eagles only show up after it is killed by Bard. It seems highly probable that eagles would not wish to hang around where there was a dragon flying about. Similarly, they only approach Mordor after Sauron, and with him the Nazgûl, have been defeated. An air defence system consisting of a Palantír-based DEW line plus winged nazgûl would probably be impenetrable. True, the winged nazgûl are only introduced once the fellowship have already sent out, but it is not unreasonable to suppose that Sauron had other airborne assets, and that the air at least in Eastern Middle-Earth was as dangerous as the ground.
It is explained by Gandalf, in The Quest of Erebor, that his involvement with Thorin's expedition in The Hobbit was motivated by concerns over air-power — specifically that in a war, Smaug could be used to attack Lórien.
If you have a life and therefore are ignorant of these matters, Wikipedia is staggeringly comprehensive.