We are at a point where the increasing professionalism in the women's péloton is seeing a greater move toward parity with regards to many Classics. Stage races are including longer stages, the UCI has increased the maximum average stage distance from 100km to around 125km, and lots of one-day races are becoming longer or including more obstacles - take the Ronde van Vlaanderen as an example, which has increased from around 130k to 160k over the last few years - as the strength in depth of the péloton is increasing, meaning it takes more to break the race up. I know that Petite-Forclaz is tough enough to break up the race, but the point of the World Championships is that it is, essentially, monument toughness, and if the rest of the big tough Classics in the women's calendar (they don't have monuments, though there has been some talk of awarding that kind of special status in terms of WWT points to the Trofeo Alfredo Binda due to its age and prestige in the women's bunch) are moving up to 150-160km kind of distance, a 120km World Championships is pretty weak.
To illustrate my point, here are some major championship road race distances in the last 10 years.
Mendrisio 2009: 124km
Geelong 2010: 127km
København 2011: 140km
London 2012: 140km
Valkenburg 2012: 129km
Firenze 2013: 140km
Ponferrada 2014: 127km
Richmond 2015: 130km
Rio 2016: 141km
Doha 2016: 134km
Bergen 2017: 153km
Innsbruck 2018: 156km
Harrogate 2019: 152km
Look at how the distances creep up when the WWT comes in, and we get more races at a solid level and more women able to make a respectable at least living from the sport. We have seen members of the women's péloton actively demanding longer and harder races, because they a) are fed up of being patronised, which is how many of them understandably see the persistence with short distances and races which omit the main obstacles, and the pattern of giving the men a much more interesting parcours, such as the ITTs at Bergen and Innsbruck, the Doha and Innsbruck road races, the Tokyo Olympic course, and events like the RideLondon crit and La Course; and b) because they want to be able to put on a show that can encourage people to tune in more and make the races more exciting to follow - the women regularly put on some great races, but when the ones that get the best coverage are 65km crits in London or Paris with no obstacles and inevitable sprint finishes, it doesn't let them show that. The Women's Tour raised the bar in terms of marketing and, although live, quality of highlight coverage a few years ago - but at the same time, the course design was very poor for the first couple of editions, leading to a race which didn't live up to the hype that the presentation about its swift-growing importance suggested - Emma Johansson literally told the organisers she wouldn't come back unless they designed a better course. Annemiek van Vleuten did the same to the Giro organisers in 2017. Cille has questioned unequal parcours designs and not being given the same opportunities to make an exciting race, Ash Moolman-Pasio has blogged on the subject, and van Vleuten has challenged the 2020 Olympic Road Race course. Gracie Elvin was less critical of the course, but criticised the restricted péloton allowed in the Olympic Road Race.
Similarly, look at de Ronde in recent years. From 2009: 132km, 119km, 130km, 127km, 127km, 139km, 145km, 141km, 153km, 153km, 157km (19% increase).
Ronde van Drenthe from 2009: 138km, 136km, 133km, 133km, 133km, 147km, 138km, 138km, 152km, 157km, 165km (20% increase)
Gent-Wevelgem from 2012: 114km, 112km, 115km, 117km, 115km, 146km, 143km, 137km (20% increase)
Trofeo Binda from 2009: 120km, 130km, 121km, 131km, 121km, 124km 124km, 123km, 131km, 131km, 131km (9% increase)
GP Vårgårda from 2009: 132km, 132km 132km, 132km, 132km, 132km, 135km, 141km, 152km, 152km, 152km (15% increase)
Other new races have either come in at longer type distances, or have swiftly grown. Strade Bianche has gone from 103km to 136km in 5 editions, Brabantse Pijl has increased from 122km to 137km in 4, and Liège-Bastogne-Liège has been introduced at 135km. Admittedly Amstel Gold and La Course are on the short side, and Flèche Wallonne remains in the 120km range, but I attribute that more to ASO's intransigence and reluctance to push the women's side of the sport in recent years than anything else. You can see a clear tendency towards longer races and tougher races if you monitor the women's péloton and its parcours over the last decade (there was something of a dip as a lot of the established names and the interest associated with them - Brändli, Luperini, Armstrong, Arndt and so on - fell away in the late 00s and early 10s, and a lot of long stage races that had been spluttering along died off in that period, like the Tour de l'Aude), and so among that, a one-off shorter Worlds mightn't be quite SO bad - but still a bit galling - but set alongside the Innsbruck debacle, Doha, Bergen, and especially now the insult of a Tokyo course, it feels like a pattern is not just emerging but has emerged here.
Or, to put it into a more simple explanation: the World Championships are theoretically to confirm who is the best. And as the overall quality of the péloton increases, it takes a harder race to satisfactorily isolate the very best from the very good, and therefore the difficulty of the World Championships relative to the rest of the calendar should be maintained, in order to ensure that they achieve their goal and maintain their prestige. As the rest of the calendar is increasing in distance and difficulty to reflect changes in the professionalism and depth of the péloton, so the World Championships therefore should follow suit to justify their prestige and esteem.