I think the Democrats are in a pretty tough political spot with this one, partly because the Republicans have so successfully shifted the goalposts that a lot of the views expressed in this thread are probably genuinely representative of what many people in the US actually think - that this report is somehow exonerating and not a completely damning call for impeachment. But also because the Democrats backed themselves into a corner by repeatedly saying "wait for the Mueller report", when almost all knowledgeable commentators have for a long time been saying that the real danger for Trump is from his financial entanglements, which were outside the scope of the Mueller investigation. I think there was an assumption that Mueller would go beyond his remit to look into a lot of the broader potential criminality, rather than farming it out to other agencies, resulting in many people simultaneously having a) not believed for a very long time that there would be any finding of collusion or conspiracy or co-operation against Trump concerning the direct interference with the election, and b) thinking that the Mueller report would provide the final answer in relation to all areas of concern. But then to be fair to knowledgeable commentators, it was pretty much gospel before the Mueller report was finalised that it could not be everything everyone hoped it would be, that it should not be relied upon as the basis for taking action against Trump, and that Democrats were making a mistake by setting it up to be.
However, it would be a dereliction of duty to not impeach Trump simply because it would be politically difficult to subsequently secure a conviction. There is moral value in taking clear condemnatory action, even where it will not actually oust Trump from office.