While there are problems, I don't think this is as bad as you are making it out to be. Xorlo did not change syntax. The cmevla-brivla merge (if that is semi-official now) makes a minor change in syntax; basically LA works the same as LE did to begin with, which is pretty much exactly what you would expect. Perhaps we could compile a list of the completely new selma'o that actually get used in practice.
I know I in particular have made a point of trying to use existing selma'o with my coined cmavo. Four of my cmavo in JVS have a selma'o I made up, two of these cmavo being in the same selma'o. Details:
{jai'a} was made for fun because I saw a use case for it, but it is only useful in the same way that {jai} is, and is much less frequently applicable.
{no'oi} and {po'oi} were made for symmetry back when I was actively working on fancylojban-ish stuff. We don't really have the brivla to make good use of them right now, and I doubt we will anytime soon.
{ju'ei} is quite useful when it is desirable, but that is infrequent. Indeed I can't think of a situation where I would want to use {ju'ei} in a literal translation of well-written English, because in English this is either bad style or simply unintelligible.
My remaining nine cmavo all use official selma'o, specifically ZO, ME, LAhE, NAhE, KE, XI, ZOhU, LE. I would strongly encourage people with ideas for cmavo to try to twist them into existing selma'o if at all possible.
The unofficial selma'o I have actually seen a fair bit in chat: ZOhOI, LOhAI/SAhAI/LEhAI, MEhOI, ZEhEI. The rest? Easily able to be ignored for a long time, in my view.