I note that the main objection is from a Handel aficionado who is parochially upset at the standard of the Handel worklists (and fair enough too). I think it helps for worklists to have as a sponsor an editor with a good working knowledge of the composer’s œuvre (from which I would absent myself from that qualification, in terms of Handel), but at the end of the day there are over three hundred composition lists of varying quality, accuracy, and completeness, and not every such worklist is going to necessarily have an expert overseeing the list with the free time to keep it up to date. Like WP itself these lists are works in progress, and anyone taking the time to edit one of them should be looking at other sources to see what information is currently omitted, but might be of use to consider adding to the page. The mantra of "Only add information to articles that reasonably assists IMSLP readers to locate scores" is only useful as far as one can define the word "reasonably", which relies on knowing how IMSLP users use the site to find works, and what pieces of information they are searching for, or utilising to assist that search. The choice of what information to include and what to exclude is the sixty-four thousand dollar question, and even the best organised of the worklists isn’t going to please everyone.
One small example: in attempting to track down a curiosity earlier today, I wanted to look through several large worklists for specific key signatures to help narrow the search, but none of the category of works had that type of information recorded in the worklist itself (whereas another composer’s worklist has some of that sort of information listed, but being a work in progress, doesn't yet cover all of that composer’s œuvre); one would have had to look at each individual work page to check key signatures.
Obviously the unnecessary duplication of work is an undesirable time sink (and many of us are busy with other time commitments), but if the alternative is to leave the compilation of worklists solely to pay-for-access websites such as Grove, then by all means let us have worklists, even if they are not always as accurate or up-to-date with the latest work additions.