If you can afford it, then yes they do exist. IB (interactive brokers) [to name one of a few legitimate] min £10k non US resident or as a US resident £1M in assets will grant you access.
But, as you quite rightly assume, many many retail brokers offer fabricated ECN accounts which are running off of an underlying market maker or in house settlement business model. But, let’s not forget that this is not necessarily a bad thing? It’s not cheap to offer true ECN and the broker’s that do offer true ECN rely on the real relationships that they hold with thier LPs.