To be fair , it worked quite well for Adobe products ( most of them are now using a monthly subscription scheme ) despite all the dissatisfaction voiced by some customers at first. It is both good for Adobe and good for the competition. In fact allowed some challengers to be profitable when everybody pirated Photoshop before as 95% of people using it only took advantage of 1% of Photoshop features. It will be a good…
You will always find some (edge) case who can profit from these kind of schemes - an amateur photographer for example with Adobe CC or somebody who uses all the jetbrain tools - but there are a lot of cases that are a different and really don't have any benefits of using SAAS.
In Flanders we have a saying that goes a bit like this: "all small things makes on big thing". The personal problem that I have is that if I would add all those "inexpensive" subscriptions of services it will add up very fast to a point that it is becoming really expensive. I don't buy all software in a single month or can even wait for upgrading if an older version is good enough for me, with SAASS that is not the case.
But I have the same opinion that this race to convert all commercial software to SAAS will be beneficial for OSS alternatives. Personally I would even go as far as donating (or crowdfund) (for the same amount that I would give to jetbrains) to an OSS project, if that means that I would get an alternative that I don't need to "rent".