1. There is no absence of people opening the kind of torrent indexers, which you have in mind. In 2010s there were 5-10 such sites launched each year, even nowadays there are at least a few new indexers yearly. Almost all are closed within a year or two (at most). There are reasons for that, some are less obvious than others.
2. Most likely you will close your site after some time as well, here is why:
2.1. It will be difficult to find a hosting, which will tolerate it. Forget about Linode or Digital Ocean or any similar hosting providers - they will suspend your server (first) and account (later) after receiving a few automated DCMA emails. You can use some "second-tier" providers for some time, but eventually even they will get tired of you, you will be out the moment they receive the first paper letter from some law company, which represents some movie company or alike. You can use proxy servers or some other arrangement for some time, but eventually you will decide that it isn't worth the effort.
2.2. The same thing is true for domain provider. Yes, there are a few, which are more resilient, than others, but don't expect that they will protect you and your domain indefinitely for $15 per year. If your site is popular enough - the only option may remain to register a new domain every few months and hop between them. Eventually you will get tired of that. It may take half a year or a few years, but you will.
2.3. There are no money in torrenting nowadays. Forget about ads or donations - even thepiratebay cannot earn money that way, you will not be able to do that either.
2.4. Sadly, torrents are not that popular nowadays as they were 5-10-15 years ago. Some people still use them, but in most developed countries that's more like an exception, than the rule. The rule is netflix, spotify and alike. As a result, if you imagine large and happy community of users around your site - just don't, most likely there won't be any.
2.5. Don't expect just to launch a site and rest. You will spend at least 5-10-20 hours per week on its maintenance (fixing bugs, importing/cleaning data, adding new features, etc). It will feel fine at first, but more and more tiring as the months and years go by. Eventually you will get bored and stop any maintenance. Users don't like old/unmaintained sites, so they will be less and less interested in it. Eventually you will decide, that it isn't worth the effort to run it at all.