OK - here are a couple thoughts regarding to your thoughts
You are right - QCad is extremely capable and I was looking for something like that for many many years. The price-performance ratio is more than excellent and the program helps me to get ALL my projects done. If I have to build a transmission or do I have to plan a skyscraper ... QCad is on my side to make it much much easier for me.
Is QCad perfect - no! Nothing on this world is perfect!!! Will it be someday perfect - no - not for everybody! But we can try to bring it more and more in the direction to be perfect.
Do we need to keep adding feature requests - yes! But I think that is not enough. I think we need some kind of measurement to get an idea how important is that requested feature for the QCad community. I think it would be nice to have some kind of vote possibility so that the QCad team can work on a priority list. It would reflect what the User is asking for and will save some time and workload for not so important feature ...
Workarounds: It is really nice to have a workaround for something what QCad is right now not capable to do for as. But honestly why I'm using a Cad Program - because I will/have to be more efficient, more accurate and more flexible than an "Old time" Drawing table guy with two rulers, circle and Pocket calculator. I'm an old school drafter and I know how I have to make a geometric construction but I don't like to transfer this knowledge 1:1 in the digital world and have still to work with construction lines etc.. If I pick up your example "Tip - Draw a Circle tangent to 2 circles" (what I really like and hope that you will keep doing that) then I hope to get from my CAD Program all the basic work done. Maybe you like to make a new workaround: "Draw a Circle tangent to 3 circles" ... I'm kidding but I'm expecting from a CAD Program that I just have to identifier the three circle and it will calculate the center and correct radius to put this circle tangent in the middle of the other three circles. Have you ever done it with a CAD Program - it is amazing!!!! Have you ever done it with a Drawing table machine ....................... ouch
It looks so easy witch CAD - but think about the Program Code what you have to build just to handle 3 Clicks with a mouse ... again ouch
Next question is - who need a feature like that? OK - counter-question: Who is using more than 5-10% of MS-Word? Maybe 5% of all User Worldwide. Why is MS offering a program with so much feature - just because that is the way to sell so many copy's. Makes me an overloaded writing or CAD Program automatically to be a good Book Author or engineer - NO! It is just a tool" Do we need good tools - YES!
Back to your question: "How many features do we need in QCAD?"
Enough to have an easy job on the routine work - but not everything what is possible!
That means you are absolutely right: It is a question of balance
My personal experience with something like this became also my motto:It is much easier to criticize something what is already done - instead of making it better - at the first time - by myself!