Yes that's true. But when you have an unconfirmed transaction and you use blockchain.com as your main wallet or any other wallet that doesn't support those features, simply use your seed or PK in a client which has the cpfp/rbf features , then you are good to go.
You can't replace a transaction by higher fee unless you have enabled it already. In Electrum, you have to enable it manually & when you broadcast a transaction, you have to choose whether or not you are liekly to use RBF in that transaction later. Importing PK or seed will not work I guess since you already have released the transaction.