I am not sure the issue here is really what features are or are not available in the free product.
From memory the product started out as free, however it must have been obvious that position was unsustainable in the long run so a commercial version which differentiated its self from the free version was not only an obvious choice, but I would have said a essential choice.
What I think is the problem here is perception. In the early days all users were free users and the question was raised on this forum when the first commercial version appeared, will there always be a free version. 3CX said yes, there will always be a free version of the product. Now they did not need to make that commitment but chose to. I would guess they thought it was to their commercial advantage to keep users interested in the product.
Now as has been said by others in this tread, if get something for free you can not expect it to come gold plated, fully serviced and to the latest specification. However you might expect to keep what you already have, the current features.
By leaving a free version but making it practically unusable you give the impression of being both devious in your intentions and dishonest in your original commitment. 3CX didn't reply to the original question of will thee always be a free version with yes just about, it was simply a yes. Most reasonable people would read into this, yes, this product will always have a developed free version you can rely on so keep on using the product and helping us develop the product. The current position now gives the impression that 3CX don't need you anymore unless you buy a license so you can go away now, thank you very much.
I don't suppose that removing another feature will increase license sales anymore than leaving features in will reduce license sales, it does however create a bad impression and waste the good will built up with users over the years.
As an earlier post says, the essential nature of a PBX is connecting lines to extensions and visa versa. The two basic tools for this is dial plans and ring groups. Fancy music on hold, call parking facilities and conference facilities are definitely an enterprise feature, rings groups are not an enterprise feature, they are an essential feature of any PBX.
I am not a free user of the product so its feature list is not really relevant to me but the continuing good reputation of the product and company is. What I do think is essential action by 3CX is clarity on their position. Either put back the features that have been whittled away in the last updates from version 9 or simply remove the free version and replace it with a simple time limited trial and clear position that all users pay for a license. It might offend those who use the product for free, it may even reduce the future user base but at least those users will know where they stand. They can go and find alternative solutions to their needs and we won't keep seeing threads like this appear on every major update.