[Long-time reader, first-time poster here. Be gentle.]Short version of question
: Can sieving ground espresso eliminate the need for a high-end grinder, particularly for home use? Said otherwise
: What, if anything, prevents us from achieving an ideal particle distribution with a cheaper grinder and a pair of sieves?
Before elaborating, I realize there are a few known issues and inconveniences about using sieves:  using sieves slows workflow, which might make sieving unrealistic for professional settings;  even when saving "fines" or "boulders" for other brewing purposes, sieving espresso will create some waste;  because of issues like static and clogging of holes, sieves don't eliminate all of the particle sizes they are intended to separate, which means making a science of sieving is not perfectly precise. For example, using a 200-micron sieve will not likely remove many or most 150-199 micron particles.  Even with the introduction of the Rafino—which I've pre-ordered—sieves are an added expense that negate some of the cost savings from not investing in a better grinder.
These caveats aside, here's the reasoning behind my question:
The long-standing consensus has been that the mark of a good grinder is a narrow particle size distribution. At the same time, notable figures such as Matt Perger have analyzed the best performing grinders (notably the EK43) and discovered that while they have a relatively narrow particle consistency at the target grind size, these grinders also produce a large number of "fines", or particles well closer to turkish than espresso. This discovery would seem to betray the belief that narrow particle distribution makes for the best coffee in general and espresso in particular. Perger's conclusion (https://baristahustle.com/grindingthoughts/
), however, is that though fines CAN contribute to poorer extraction when particle distribution is very disperse (as with bad grinders), fines do not INHERENTLY contribute to poorer extraction. More accurately, the presence of fines in tight particle distribution (as with EK43s) allow us to reach higher extractions (>25%) in a reasonable amount of time; though fines have been said to instantly overextract, that overextraction is what contributes to the EK43 getting very high and delicious extraction percentages. Said otherwise, the problem is not with fines, but rather with how we extract them in the brewing process. In the end, Perger's conclusion supports the superiority of the EK43, which would seem to thwart my cheap agenda of finding a sub-$2k alternative for making excellent espresso.
Yet what doesn't make sense about Perger's reasoning is this: Even with the EK43's amazing particle range (fantastic particle consistency, yet relatively more fines), it's unclear why this would be better than a sieved grind with a more consistent particle size range, but just adjusted to a slightly smaller than the EK43's mean grind size. That is, if the benefits of the EK43 is that is produces more fines and therefore increases extraction rates, why not simply sieve a grind that is somewhat closer to turkish?
Perger's own data on the typical range, mode, and mean size of the EK43's grind distribution is this:EK43
: Range: 10 - 800+ microns; Mode: 295.5 microns; Mean: 237.3 microns
With my $200 Baratza Virtuouso, apparently I could never hit those numbers. BUT, with a few sieves added to my setup, I may be able to hit something like this:Sieved
: Range: 150 - 300 microns; Mode: TBD; Mean: 210 - 240 microns
The average/mean particle sizes in these two scenarios are similar; both are capable of achieving >25% extraction. But whereas the EK43 grind achieves this quickly because of the presence of fines, the sieved grind may indeed require more time to fully extract. So, the EK43 succeeds in  extraction and  brew time, and also does far better than any other un-sieved grind with  evenness of extraction. Yet it my hypothetical sieved setup, I would appear to actually beat the EK43 in  total extraction percentage and  evenness of extraction, though perhaps being slightly slower and therefore losing on  brew time. More still, if brew time were a real issue, one could simply reduce the mean particle size with smaller micron sieves. That is, the sieves could match the EK43 in  extraction and  brew time while also BEATING the EK43 in  evenness of extraction, because it would have a tighter particle distribution.
In short: It would take more time and definitely some experimentation, but even with a low quality grinder, it seems like one should be able to artificially create an ideal particle distribution with sieves.
All that said, there is one other concern I've heard floating around, which I have no way to verify or falsify: Espresso brewing NEEDS a wide range of particle sizes in order to maintain the structure of the puck in the brewing process. That is, one could perfectly make every particle in one's dose exactly one's ideal size (e.g. - 200 microns), but the uniformity of the particle distribution would block the flow of water somehow. This seems to be why some have argued that sieving is appropriate for all types of brewing EXCEPT espresso. Though I have no way of disputing this claim, this seems to be a convenient fallback in support of high-end grinders.
This is much less scientific, but in the end if feels like there is a lot of dubious and motivated reasoning in support of the particle distribution of high-end grinders: "You want your grind to be consistent, but not TOO consistent. What you really want is the particle distribution that happens to be produced only by grinders with 98mm flat burrs." Sieves may have their issues, but it seems that the ability to manipulate particle distribution in whatever way you want with a sieve would allow you to achieve an optimal grind for espresso.
Has my reasoning gone awry? Have I misunderstood something? Seriously, I'm not trying to build some grinding manifesto or to take down Matt Perger. I'm mostly curious if there isn't a way cheaper option for home baristas to achieve excellent espresso grinds.