I don't believe EM4 had a particularly "strong" modding suite of tools for it, if not for Oleg with Z2 I don't think it would've went anywhere (sure blender came much much later, but without Z2 it would not have gotten that far). 5 is in much the same boat as that goes, the dev tools frankly are clunky, nowhere near well documented enough and the game it's self has many flaws: This is pretty much where em4 was when it came to be; the diff being that em3 carried over much of em3's modding utils (and format) so that eased the process even though to my eyes em3's editor was more "complete (most the stuff in it actually worked).
Em5 would require people who are figuring it out to be more open with how-to do it along with "ease of use" tools external from the devkit they provided to make a go of it, plus people who would actually want to take the time to do it. Most people from em4 were expecting em4 with better toys/graphics to build with but to retain the existing structures and such, that really was wishful thinking but one would've hoped they at least tried to detail how to go about it better.
To find the "heyday" of the community you really gotta go back even further to around 10 years ago when there were far more people modding and far more interest in doing it, itch's arrival brought with it some new models but really did not see anything other than visual updates: the game saw it's best strides when people were still finding new/exciting things to do with it. Whether EM5 does anything who's to say, that's up to the devs that want to tackle it and try to mod it. Comparing emergency to other games out there really is a fool's errand because it filled a fairly niche market, one which as of to date I've not seen much in the way of competitors for: First persons and 3rd persons are not what emergency tried to be and as such should not be compared anymore than "call of duty" would be to RTS.