I think “terrible” is a matter of perspective. Also understand that the person you’re debating this with has a long-proven admiration of Epcot in its classic form... Just look up Epcot’s 25th anniversary for my credentials.
Here’s the thing... Classic attractions like Horizons and the original Journey into Imagination were amazing. But by the end of their lifespans they struggled to attract riders. The same is true with both Universe of Energy versions, World of Motion, El Rio del Tiempo and The Seacabs in The Living Seas. These attractions need consistent ridership to justify operation. There are no theme parks (past or present) that have been able to justify operating major attractions (at major expense) without ridership value to offset the cost. Attractions that fall into this rut are either retired, rethemed or removed outright. It isn’t a question of quality—it is a question of appeal. Timeless attractions maintain their appeal—the majority of the attractions in Fantasyland, Adventureland and Frontierland at Disneyland Park and the Magic Kingdom have not been replaced, only plussed because of that enduring appeal.
It is easy to gripe or idealize what audiences should want to experience or consume but the proof is always in the numbers. When the appeal has worn off, choices have to be made. Fans may not always like that expansion space and existing attractions are turned over for IP-based projects, but that is what gets guests through the turnstiles these days. The old edutainment approach on its own stopped succeeding in the 90’s... It had to be supplemented with IP and thrill to get guests to come to the park. The things you like about current Epcot couldn’t exist if the popular attractions you call “terrible” hadn’t been added to the park when they were. It was those “terrible” attractions that evidenced a need for more characters, more thrill and more for families... Without those, that park would continue to struggle until more drastic decisions might have needed to be made.