Let me give you an analogy.
I would love to be a model. I can't see any reason why I can't pay to boost my application to the top of the list of a modelling agency, because I really, really want to do it.
The only problem with this is that I'm not good looking enough to be a model. Thus, should I be successful in becoming a model, unfortunately the clients that any modelling agency connect me with are going to be pretty underwhelmed, inevitably wondering why they've sent this presentable but completely unremarkable male to work with them!
Furthermore, I find it hard to believe that modelling agencies would appreciate my application being boosted to the top of their list, regardless of how passionate I am about the role, given my complete unsuitability to work as a model!
This is a far-fetched example, admittedly, but it does illustrate the abject stupidity of this policy. The degree to which you want something is completely unrelated to how much you deserve it, or are suited to it. I want every job that I apply for. I don't apply for something if I don't want it. By this rationale, I should boost every single application that I ever make, otherwise I'm indicating that I'm not really bothered.
This is the first time, of which I'm aware, that the platform has actively implemented something that is universally bad for both clients and freelancers. It now costs more money to submit worse applications that are less related to the actual qualities required to do the job. And clients are presented with a misleading and less effective indication of who is well-suited to the position.
In fact, in the long run, this policy will simply annoy lots of clients and make them less likely to use the platform; thus, generating less revenue. Until it's reversed. It will have to be reversed, as it is a farcical policy that works against everyone who uses the platform, not to mention any notion of fairness or authenticity and the overall credibility of Upwork.
Apart from that, great decision!