I looked at brief descriptions of quite a few L2 projects. Isn't there at least one or more which do not use new tokens, they are a "true layer on top" which helps give Bitcoin more powerful smart contracts?
The only "true layer on top", sufficiently developed and actively researched and maintained is Lightning. Everything else is just another blockchain.
Taro and RGB don't have their own native token but try to stick and integrate more with the Bitcoin Blockchain doesn't mean itself that Bitcoin supports advanced smart contracts.
Both Taro and RGB are not reusing bitcoin as currency. They are networks that issue new assets. You cannot enter with a bitcoin amount in any of those networks and be certain that you will return back on-chain with the same amount. There's no on-chain transaction which will can be broadcasted in case you want to unilaterally return some of those assets for bitcoin.