My 2 cents is that
a) as Ashley said, people are sceptical of Browser-based software and don't value it as much as desktop software (kinda like mobile apps that can't ask for the same price with same functionality as desktop apps)
b) there's a certain subscription fatigue in the marketplace in general (look at Streaming services, etc.) I'm sure Scirra will argue strongly against it but they have to be really careful to not outprice themselves out of reach of their target audience. Sure, Game Maker etc. has subscriptions too but they have a bigger brand, more hit games to back themselves up, they promise you exports to consoles (which even then isn't as easy as they make it seem), etc. I don't know however, if you'd have substantially more users when charging $79 per year vs $130 and the danger could be that you lower the price but don't gain any users which would be basically harmful to the company.
c) The No-Code aspect CAN be seen as something that will hold you back. I also think it's much less of a sales argument than people think because most beginners still flock to Godot now, which is using a Scripting Language etc. Instead of Ease of Use i'd rather focus on emphasizing SPEED of use. Meaning Construct is the only Game Engine that let's you make projects almost at the speed of thought thanks to its revolutionary approach to visual scripting. There i'd rather compare the event sheet system to the more common node based structures that we see, that lead to quite unwieldly results.
Some more random thoughts:
Personally i don't think there's anything wrong in having tools that are more suited for smaller projects at all. I mean it becomes more and more clear nowadays that there's actually a DEMAND for smaller games, because of the overabundance of offerings. People simply don't have time to play every 200 hour AAA game anymore and more often than not, they're actively looking for something that will keep them entertained on a rainy sunday afternoon.
I think Scirra could probably think about doing more sales promotions. Stuff like get the first three Months for 50% off or something like that. Just to get people to sign up and hopefully convince them enough so they stay on.
I'd also forget about all the petty "We're better than GML" stuff because the average user who'd use either engine really doesn't care much about that. Also you can get onto thin ice very quickly. These kind of posts were never well received either and don't come across as very self confident from Scirra's side.
I'd rather always focus on the vision for the end user. Know their dream, i.e. creating your first game from your bedroom but no idea where to start and sell them the solution to their problem. Know what values the brand stands for (making games should be accessible) and hammer that home. Simply JavaScript > GML won't inspire anyone but being the number one address to put people on their path of game development will.
I think if Scirra works on their storytelling a bit and caters their marketing activities (and website) a bit more towards that it would definitely help. I agree however that recommendations will always work best but even those can be much more amplified. Instead of weird spinning cubes on the homepage, why not have some quotes by people who actually made and published games with the engine and what they love about it?
Self Promotion is always the hardest which is why even ad agencies often get outside partners for their own marketing because an outside view always helps. I think maybe investing in some consulting, even if it's just a workshop or something with the whole Scirra Team would be something to think about. Just to get an evaluation of the website, the social media strategies, the sales channels, etc.