According to Messari Cardano oscillates between 2nd/3rd most active crypto
https://messari.io/screener/most-active-chains-DB01F96B
Given the head start for Ethereum I would call this very successful in terms of adoption.
Re:I would like a job writing Haskell
by pcthrowaway on Tuesday February 08, 2022 @05:25PM
(#30265718)
Ethereum and EVM compatible chains are at least 4 years ahead in terms of smart contract activity. Cardano just enabled smart contracts in September of last year, and there's been very little success in terms of usability so far; network scaling upgrades are slated to roll out over the next few years, and the dapps that have deployed don't really work without them. For context, Sundaeswap, a long-awaited DEX just deployed roughly 1 week ago, but people trying to make swaps may have to wait days for their swap to execute, which isn't very ergonomic.
The increased activity from people trying to make transactions with Sundaeswap has resulted in sluggishness all-around on the chain as well, because Cardano doesn't have the concept of gas bidding for priority
Haskell actually is used for smart contracts on Cardano (which is also written in Haskell): https://github.com/input-output-hk
They haven't been very "successful" yet in the sense of mass adoption (even as far as smart contracts go, EVM-based dapps have multiples more users), but I think this is because of design choices in how the blockchain works moreso than using Haskell for implementation, which limit the usability right now.