I have no question regarding the security level of Bitcoin for now, except if you handed over the private keys or mnemonic phrases carelessly to someone else or a third-party source. But BTC isn't perfect yet due to the quantum threat. There must be some sort of ways for Bitcoin to switch into quantum resistant blockchain or something like that. But who knows? We will see that outcome in the future though.
Two factor has already been introduce accessing online wallets need a confirmation on a device or to email before it can proceed to transaction. However, private keys may drect to the wallet so this is one of thr crucial way to open a digital wallet. If it will be disclose to anyone or just being skim by a fake website then pretty sure it will be the end of crypto holdings. So, one must careful on fake sites that even their sites had the same as with the original web address so one must be keen on every letter or symbols in web address. Better to bookmark a site instead to direct the site once wanted to access.