"nobody loses all the time" is charged with irony from start to finish.
First, the title (which is also the opening line) has an ironic relationship to the events of the poem. The poem's protagonist, Uncle Sol, is so unlucky that he does appear to lose "all the time." Only in subtle ways does Sol emerge as a kind of winner: for example, lots of loved ones mourn him after he dies. But then, it's also rather ironic that most of his good fortune only comes along when he's no longer around to appreciate it (as when a benefactor throws him a "splendiferous funeral").
Likewise, Sol's final farming venture is "start[ing] a worm farm" in the grave. Of course, this is just a comic euphemism for becoming worm food; Sol isn't actually trying to "farm" under the earth. The speaker is cheekily presenting Sol's death as one more attempt at success, when in reality, death marks the end of all such attempts. Sol was a "born failure" and he died a failure, at least in financial terms.
There are other, subtler ironic touches throughout the poem. For example, the speaker frames farming as a self-indulgent "luxur[y]" compared to a career in show business, when most of the world, arguably, would see it the other way around. This unexpected framing underlines the idea that Sol wasted his true talents while doing something he had no talent for. Later, "chickens" eat Sol's "vegetables" and "skunks" eat his "chickens," so that Sol suddenly finds himself with a "skunk farm." Again, the phrasing is loaded with irony: Sol doesn't have an organized "farm" of skunks, he has a plot of land overrun with skunks.
In general, the poem's ironies turn Sol's sad story into an entertaining comedy, while presenting a wry perspective on life in general. In the end, the claim "nobody loses all the time" can be read as pure verbal irony (that is, the speaker might mean mean the opposite of what they're saying). But the speaker might also be partway sincere. They might feel that even a life as loaded with situational irony as Sol's—a life in which nothing works out as you hope or expect—has some redeeming elements.