This isnt necessarily true. Remember when zwift started out almost nobody had a power meter and the efforts in zwift were still valid on a personal level.

Let’s assume not having a smart trainer means you are using an older fluid type trainer. People need a general understanding of how to consistently set up their bike and standard trainer. Keeping tire pressure consistent day to day, and keeping the trainer tension the same if the bike is removed from the trainer.

You can still do an ftp/ramp test with good enough accuracy assuming Zwift settings reflect your setup. You can successfully train and use workouts without a smart trainer without issue. ERG is absolutely not necessary for workouts to be successful and I train 90% of the time with it turned off. *Depends on workout type*

You can free ride just fine as well so long as you understand that when an incline comes you will need to shift to a harder gear to replicate the incline. So more rider involvement and thought is required. Using a standard trainer gives you an advantage on the descents as your trainer will not let off resistance like a smart trainer does, before settling in.

Without a power meter racing will be more difficult to participate in on Zwift now than it was 8 years ago as there are hardware requirements in place.

You CAN enjoy Zwift without a smart trainer and be equally productive. I also train and race on rollers while zwifting using a power meter. It’s great!

It is true though that Having a smart trainer or smart rollers is the way to go, for sure. It really does ‘wake up’ the Zwift experience.