There is nothing in Scripture to support dead people throughout time as being able to now pray on our behalf.
They are dead and Scripture shows no way for those in Heaven to speak on our behalf.
Scripture indicates, those in heaven are aware of the prayers of those on earth. This can be seen, for example, in Revelation 5:8, where John depicts the saints in heaven offering our prayers to God under the form of "golden bowls full of incense, which are the prayers of the saints." But if the saints in heaven are offering our prayers to God, then they must be aware of our prayers. They are aware of our petitions and present them to God by interceding for us. Prayers are not physical things and cannot be physically offered to God. Thus the saints in heaven are offering our prayers to God mentally. In other words, they are interceding.