This is not quite correct: true, there is quite a number of small companies that disgracefully sell low budget productions of Elektra or Aida by simply cutting off on the number of players or eliminating the choir. But others, with some well planned budgeting and smart choices, are able to put on great productions.
Take the recently defunct Gotham Opera in NYC: the company sunk probably due to some bad management, but the productions they had were far from amateurish. LoftOpera went head to head with the Met with a production of Barber and they got praised by the New York Times not only for their effort but for the high level of the outcome. Peter Gelb himself had nothing but good words for them. On this side of the ocean, OperaUpClose in London is getting rave reviews for its bold take on classics as well as new works.
In a way, small opera companies have most chances of succeeding than their bigger sisters (look at what happened to New York City Opera), mostly due to the fact that their budgets are more sustainable and they often present niche products, whether they do traditional operas in unusual spaces or less known/contemporary works. Audiences are often attracted by their shows because of the less-formal-feeling and the idea that they are more part of the show instead of just looking at it from a distance.
The real worth of small opera companies is their capacity to refuel people’s attention on this art: they know they have to rethink the concept of traditional opera in order to survive, break the rituals and engage new and old audiences in a time in which it seems to be needed the most. Something the big theaters way too often delegate to weird and unimaginative staging, hoping to create some buzz and sell some more tickets.