Lightning Network will only ever see utility on times of high-volume transactions on the network. It will not get much of its sought-after mainstream adoption due to its added complication on the transaction process. Either way, I'm pretty sure LN will have its official uses side-by-side with the network, and I'm just not seeing it replacing the network as a whole.
It's the complexity of LN transactions, which stifles the network's growth in the mainstream world. The Lightning Network won't be able to replace on-chain transactions if the average person doesn't know how to use it. Without user friendliness, the Lightning Network will only remain as an alternative than a replacement of on-chain transactions on the Bitcoin blockchain. At least, people have the choice to skip high fees and slow transaction confirmation times. They can either use the LN or an altcoin of their preference. What matters is that Bitcoin remains decentralized in order to maintain censorship-resistance. Unlike cryptocurrencies with on-chain scalability (like Bitcoin Cash and Bitcoin SV), Bitcoin's path to scalability is much safer as everything happens on a separate layer. If the LN fails, Bitcoin will continue to operate as usual.
Nonetheless, no one can predict the future. So far, the LN has been doing well in terms of active development and innovation. As long as it's maintained by the community, it will be able to stand the test of time. For what I know, the LN is still an experiment. Whenever it'll be a success or a failure in the long run, it's yet to be seen. With so many other blockchain networks available on the market, there might be no reason to use the LN in order to enjoy instant transactions and low fees. Just my thoughts