Estate law is a well-worked out system that has dealt with all the issues that have come up for millions of people over hundreds of years. It'd be hard to have similar confidence in a system that hadn't been around for a long time.
Personally, purely from a user experience point of view, I’d rather have an online portal where I can manage my info than have to go through a law firm each time I want to update anything. As such I feel there is a business case here IF the trust issue could be resolved.
Executing after you're dead only happens once, so it can be heavyweight.
Updating should be as lightweight as possible. One reason it's heavyweight in the current system is that, after you're dead, people who didn't get what they think they deserve can sue your estate. Often the argument is that you were under someone's influence when you updated your will. Having your estate lawyer say, "Mr. Disruptthelaw came into my office on ___ date and we discussed this amendment. He appeared to be of sound mind" is fairly persuasive to a judge. But a late-night edit to some database, even if it's on the blockchain signed with your private key, might be less convincing.
The usual way to work around the difficulty of amending a will is for the will to say "Everything in the Disruptthelaw Recovable Living Trust is goes to ___". You can move assets into and out of the trust easily.