It still violates the optimistic premise of blockchain advocates that it helps us move to a world where trust is baked into the systems.
If you live under the assumption that you're perpetually under attack unless you rigorously protect yourself, it's not really the example of trust we're promising to non-technically adept folks.
Technically the unit of measurement is hashing power, rather than % of nodes or participants, but there is an underlying 51% problem with blockchain.
The attack surface is similarly limited; they couldn't really "rob" the wealthiest wallets, but they could prevent their transactions from ever happening. They could also spend cryptocurrency they don't really have. Here's an intro:
In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. That's all it takes to completely change how much money is in my account in a "distributed" bank. I don't own it, and it's certainly not robust against demagogues.
Demagogues are by definition political opportunists who play on populism to advance their politics. If democratic elections have a vulnerability to them, so certainly do "distributed systems" where a simple majority has enough power to control "history"
If you live under the assumption that you're perpetually under attack unless you rigorously protect yourself, it's not really the example of trust we're promising to non-technically adept folks.