Fwiw, perfect too often is the enemy of good - or even great.
I think the central issue for many is the belief that "preaching the Gospel" is a divine mandate. I don't agree with how that has been interpetaped in some ways, but, scripturally, it is hard to argue against that belief, generally. There are reasonable arguments about WHO is responsible for fulfilling that mandate - a specific, relatively small subset of believers or all believers, for example. However, it is a clear scriptural mandate, given without explicit qualification. This is important to acknowledge, because . . .
Personally, I see no chance that the Church will say:
"It is no big deal if traditional missions dwindle dramatically or disappear (which is a result that needs to be considered). Whatever is cool."
I also don't think that result is desirable, from a simple Church growth perspective. Traditional missions are far too good for far too many people (and the organization) for the Church to be okay watching them slide into irrelevancy or even decrease the importance it attaches to them. Seriously, I just can't see that happening, and I understand completely and respect why.
However, missions often hurt specific missionaries, in widely varying ways. Service is important, and many members would do better on service missions than traditional missions - and many who would be fine in different missions would do better on service missions than with specific Mission Presidents. Also, many members want to serve traditional missions, show no indications of not being able to so productively, and then discover they are being hurt by those traditional missions.
Thus, I understand the need to maintain an emphasis on traditional missions while opening the door for FAR more people to do service missions or not serve missions at all but still feel accepted officially in that action. I understand why the Church can't say officially to individual members, "Do whatever you want. You tell us what you want to do; we will make that happen." I understand the appeal of that approach, and it absolutely is the ultimate example of complete and total freedom/agency, but it is nowhere close to the ideal when it comes to fulfilling what is seen as one of the most explicit Christian mandates: "Go ye, therefore, into all the world..." Thus, it becomes a balancing act.
I see this announcement as a great attempt to provide a difficult balance. Initially, when the individual meets with the local leader, the question is if the member can serve a traditional mission, with a clear, official, stated recognition that all members will not be able to do so. If everyone agrees a traditional mission should be doable, the person will be called on a traditional mission - with the explicit understanding that if it doesn't work for any reason, it can end and the person can switch to a service mission without any official stigma associated with failure (or be released completely and be done). If the decision is that a traditional mission is not appropriate, service missions are available as another official, acceptable, non-inferior option. If no mission is deemed appropriate, none is assigned - without any official censure or judgment.
Finally, I see this as a way for individual members to say to their local leaders, "I can't serve a traditional mission, but I can do a service mission." That leaves the responsibility on the local leader to process the request for a service mission, just as they can do now but with an official statement saying it is fine in far more cases than it was previously. It isn't like SLC is the one making the determination in all cases of which type of calling will be issued. Local leaders now will have a lot more authority in that area, as I understand the announcement itself.
Of course, there will be cultural crap in too many cases still. That is completely up to local culture and leadership roulette, which sucks sometimes. However, it is important that the message from the top no longer is that being "worthy" is connected directly to serving a traditional mission - or that leaving a traditional mission early is a sign of sin or weakness or faithlessness - or that leaving a traditional mission early ends one's mission entirely. This change makes the "Called to Serve, Not to Suffer" article official policy. That is important, and I love that aspect.
It is a major change, conceptually, and I understand why it can't go further right now. The Church simply can't risk undermining traditional proselyting by not prioritizing it for those whom it likely won't hurt but will be beneficial.
At least, that is my take on it.