The devs could have done a lot of things differently such as completely ignoring community feedback, etc., but they didn't. Instead they chose to actually take into consideration community feedback and improve the game much more than originally planned (better animations, more diverse locations, etc.) and add more features than originally planned (the new arena mode with progression, the improved terrain, the improved dialogue and NPC interactions which will support SG and not just Exanima, vastly improved dev tools, etc.). They're doing more than originally planned yet they do not have additional resources (neither funding nor additional developers - the funding they have is barely enough to pay for basic living expenses such as food and some of the devs have even had to take on additional work just to pay the bills... so far they've made zero profit and have had to invest their own personal funds).
All of the remaining levels in Exanima are already created and now they're working on the mechanics required to flesh out the remaining levels and finish adding content (such as thaumaturgy, dialogue, more in-depth NPC interactions/roles, etc.). BM are getting very close to having all of the mechanics and art assets necessary to complete Exanima in place and they've spent additional time to ensure the mechanics will support not only Exanima but SG as well. This wasn't the plan originally but they decided it was better to spend the time and do it once rather than redoing everything a second time after Exanima is completed and focus shifts to SG.
Claiming that BM could have "accomplished way more with the time that has passed since this first release and with the amount of money they have received as of today" is a bit presumptuous. Bare Mettle have devoted their lives to creating their dream game(s) and wasting time/money definitely isn't something they're keen on doing. It's actually rather impressive how much they've accomplished with so few people and so few resources; they're doing many things which haven't been done before even by massive development teams with nearly unlimited resources. Madoc already works 14+ hours a day, 7 days a week and has taken less than a week off from game development in the past 5 years. He basically eats, sleeps and breathes game development and I don't know of anyone who works harder than he does. The reason they've been able to continue development for as long as they already have is due to being very frugal with their funding and investing it wisely (the devs get paid less than a janitor would make for a salary and it doesn't even cover all of their living expenses). Yes, they could have made different decisions such as cutting out features, releasing buggy content, ignoring community feedback, etc. which would have sped up the process but none of these are good options (in my opinion) and I'm glad they are taking the time to do things properly.
In short: BM are making significant progress despite the lack of updates recently. Most of the things they are working on are huge in terms of what it'll allow gameplay-wise and they've already implemented all of the remaining areas in Exanima -- it's just those areas can't be released until the supporting mechanics are also in a playable state since they're required to finish the content in those areas. In the next update we'll see dialogue mechanics, another location in the story mode with almost all new art assets which will utilize the improved terrain mechanics, new NPC interactions, etc. In the update following that thaumaturgy mechanics will be introduced as well (significant progress has been made on thaumaturgy already).
Likewise, the recently improved dev tools allow BM to create new things much more quickly and to experiment more than before by simply clicking a check box or moving a slider rather than manually doing 50+ steps in order to achieve the same thing. This will save the team massive amounts of development time and allow them to be more creative at the same time. Madoc has mentioned he wants to revamp the first three levels in order to include new game assets which were created after the first three levels were released and to also include natural terrain elements which are now possible after the terrain system overhaul.