Morgan Tuck and Megan Walker were already starters when they left. Natalie Butler probably was never going to be a starter here, and went to a school where she could be a star. Azura Stevens however is a good example, because she probably would have started the next year if she had stayed, but was still drafted pretty high as a great sub on a great program.
If Dorka is the best player this year, go ahead and start her. Geno seems to grant seniors and incumbents an advantage that is probably more than I would give, but if it is decisive I think he will make the change. But I think Dorka is likely to return for other reasons.
I think both Liv and Dorka are possible long term WNBA players, but far from locks, more like marginal prospects that may not be picked in the first round, but are very likely to be able to play for pay in Europe as their floor. A Uconn pedigree as a star player on the bench or as a starter helps your chances of employment there.
A player who is fairly certain they have a WNBA future is more likely to jump into the draft. Morgan, Megan, and Azura were all in that category. Dorka is not considered at that level, at least yet. In addition she is in grad school this year, not starting next year, so presumably she is only one additional year from a master's degree, which makes staying another year (probably as a starter) much more logical.
But that doesn't mean I think she shouldn't start this year if she is better. I just think the burden of proof for Geno when bumping a senior incumbent is high but that either way, next year she is the probable starter, and probable to return.