As stated here, if blockchain is hacked most likely your coins will still be safe. Because they do not hold your btcs. But if your computer is compromised and you uses hot/online wallet like blockchain there is a great chance that you will get hacked.
blockchain.com hosts a non-custodial wallet service. they don't "hold" your BTC. that's why they can't recover your wallet for you if you lose your key/password. your seed can be used to recover your coins to any other HD wallet.
so it's not as bad as 3rd party web wallet services that actually control your BTC. but there are still some security hazards. you are prone to various MITM attacks when you use a trusted online service like blockchain.com to sign and push transactions.