Thanks for your support !

Purebasic is the first true language i learned (around 6 years ago, maybe a bit more), so it's more like a comfort zone. The programming is not very difficult, but the Purebasic makes it a bit stupid sometime. "If it's stupid but it works then it's not stupid". I (and i insist on the I) have problems with these other software :
1) I can't optimize the shit out of it very precisely (I'm very pervert about optimization).
2) They don't create compact stuff (Here I code everything by hand (lol) so i know precisely the weight of my stuff, an empty PB game weights around few Kb).
3) They need a learning step to understand the basics before beginning hard coding.
4) The software are sometime quite heavy themselves.

I could perfectly remake the game on one of the engines you mentioned, but i won't be as precise as i want on Purebasic. I'm not using complex stuff (sprite loading/display/collision, sound load/play, structures, procedures and memory management). The first steps were painful until I got a stable backend. I still have room to improve here (XML data loading for example) but that's fair enough as it is for now.

In other projects I won't bother taking care of the dev (I hate dev !!!), because why do some coding when there's people able to do that for me hurr durr
However the Hand2Hand project is a childhood dream coming true, so it's very personal in the good sense. Purebasic was natural because
1) it's precise enough compared to other engines
2) It's the one i know best
3) It's easier to handle than C, C++, Java or JS
4) Maybe not as complete as the mentioned languages, but gamedev functions are easy to use and native (so no heavy libraries to import !)
5) Not free, but I can break down a big file with smaller ones. They are all imported to the main file anyway.

Yeah i'm using the demo version because "not expensive is more expensive than free". The project is too big to enable the debugger but all separate files are small enough to enable compiling and execution. The debug becomes quite harsh because any memory problems will make the game crash without any warning (welcome to my army of MessageRequester to track down the crashing line !)

You don't need to compile a game design document to see if it works, that's why GameDesign is my hobby horse. And trust me I only need a first professional experience to be called a professional.

So to answer your question "Is Purebasic effective at gamedev" well in my opinion if you can gamedev with your ass and it works well i don't see any problems.
Although nobody care about opinion, as opinion is not an argument. Joke aside, it depends on the architecture and how it can handle graphics. Purebasic have its advantages and faults ; even if it's quite niche it's way more natural and easier. For example some languages need textures, sprites, handles, objects, etc... but Purebasic only uses integers as resources ID. While loosing the flexibility and power of Oriented Object, it gains a lot in code maintenance and coding speed. I don't know how it's made in very low level so I won't admit anything yet.

The short answer : not technically the strongest, but very easy for everyone. Maybe even easier than Python on that matter.