This site tries to explain that but I don't understand very well since it's in japanese and I don't find anything in english.
Simply, ますます can mean "more and more" or "less and less" depending on the verb it's used with. If you make it modify a verb that describes "reduction in quantity or intensity", then you'll get the effect closer to "less and less" or "decreasingly".
- 風はますます強くなった。 stronger and stronger
- 風はますます弱くなった。 weaker and weaker (or less and less strong)
- 値段がますます上がった。 more and more expensive
- 値段がますます下がった。 cheaper and cheaper (or less and less expensive)
- 部屋をますます美しくする。 more and more beautiful
- 部屋をますます汚くする。 dirtier and dirtier
Although uncommon and potentially puzzling, You can use ますます with a negative expression using ない:
- ますます元気になった。 more and more energetic
- ますます元気でなくなった。 less and less energetic
- ますます痛くなった。 more and more painful
- ますます痛くなくなった。 less and less painful
Note that "ますます良くなくなっている" is not the same as "ますます悪くなっている". The former means something was good at first but it's becoming less and less good, whereas the latter means something was already bad at first and it's getting worse and worse. (Usually something more concise like 良さがますます失われている is better for the former sense, anyway)
The Japanese article you linked says expressions like ますます減る and ますます低くなる are weird because ますます should be etymologically 増す増す. However, I think the author is overthinking. While I guess "to decrease increasingly" is puzzling in English, ますます減る seems totally fine to me, and BCCWJ actually has 5 examples of ますます減る/ますます減少する. (The author then says the Japanese grammar lacks the equivalent of "less" or "least" in English, which is true. Anyway ますます covers the meaning of "less and less", so this shouldn't be a big problem.)