WPLG being dropped from YouTubeTV, Hulu, etc. at the start isn't surprising. The network negotiates the retransmission consent rights for all the affiliates. So, WPLG was covered by the agreement ABC made with Google. No ABC. No agreement for Local 10. They will have to hammer out deals with all the vMVPDs.
To be honest, not being on YouTubeTV isn't the end of the world. While it is the largest platform of its kind by far, it has about 9.4 million subs nationwide. There are 125 million TV households in America. So YouTubeTV has about 7% of the national population. Let's assume that a metropolitan area like Miami skews slightly higher than, say, a rural Midwest market where internet connectivity may be slower. Even if YouTubeTV has 8 or 9% of the Miami market, WPLG can survive. But it might be enough to shave off just enough viewers to cause some pain.
On the flipside, WSVN's ABC feed is immediately covered by all ABC agreements once that feed is live. It will be interesting to see if it is up and running on day one. (It should be since they have had plenty of lead time)