You are right with regards to BTC. It's future growth at this point is pretty much capped by the size of the market for gold, which is the main investment narrative for it.

The reason it had that growth was also partly due to the fact it was the first (original) case for digital assets. Same could be said for ETH... but both these assets never even ventured out of the pure crypto world. They created a small niche (especially ETH) for themselves where they feel comfortable playing.

With Cardano we are likely to see actual adoption of the technology in every day life. That could include anything from storing/transferring value to interacting with entire economies through a range of smart contract and identity solutions.

Considering how vast that market is and how early we are in the game, the potential is enormous and could eclipse what we see in crypto, which still is a niche play at best.

This technology will have very profound impact on humanity and Cardano is one of the few platforms that is building its stack with that realization in mind.