Yeah I agree that's terrible the small-size graphic and strange-looking output when you try to Roll a rollable table with graphics. It's been touted as a way to do custom dice sets, and while it might be OK for a dice-sized graphic with really simple faces (like putting a Skull instead of 1 dot on a d6)... Otherwise it's really bad and could be so much better. There's no good reason for it not to show a full-size or chat-width sized image, but that's what we are stuck with. I haven't even seen a Suggestion thread to fix this.
That's also annoying how you can't roll a Rollable Table mutliple times like this doesn't work:
[[3t[Roll-Yes-Or-No]]]
This workaround does work to roll it 3 times, but is cumbersome and not good:
[[1t[Roll-Yes-Or-No]]], [[1t[Roll-Yes-Or-No]]], [[1t[Roll-Yes-Or-No]]]
So I agree with the downsides listed in the OP and replicated the issues.
I use Rollable Tables a lot for Mad-Libs style where the Table items simply have words, not images. It works well for me, for that purpose. But rollable tables could easily do so much more, with a bit of features improvement from Roll20.
It's quite sad that Roll20 Staff updates have been constantly entirely focused on D&D 5E 2024 for months and months, with no progress on system-agnostic tabletop feature additions or Forum Suggestions. Even with Jumpgate out-of-beta, this trend continues.