Catholicism has always had a teaching of “degrees of glory”, meaning that in Heaven, the saved receive rewards from God based on their merits. The Father’s House has many mansions. The difference is that in Catholicism, these mansions are all in the eternal presence of the Father, Son, and Holy Spirit. In Mormonism, these mansions or degrees are not in the eternal presence of the entire Godhead. Somehow, the Father, Son, and Holy Ghost are separated, and those in one Kingdom may not be in the eternal presence of one member of the Godhead while another Kingdom will be. Catholicism accepts the ancient teaching of different Heavenly rewards based on our merits, but also teaches that all of these rewards are in the eternal presence of God (all three members of the Trinity, who are not separated).
Catholicism has always allowed for baptism by full immersion. It was never lost. What Catholicism does do is allow for pouring to also be performed as a valid baptism, through her authority. It is always amusing to see some LDS apologists claim that Catholicism “changed” the mode of baptism, and you cannot change how ordinances are done, when they don’t even realize how certain LDS ordinances have changed in mode, the prime example being the Initiatory washing and anointing in the temple. It has gone through substantive changes in mode throughout the years, where today, it is only a “symbolic” washing and anointing, with a dab of water and oil being placed on the head/forehead of the patron, and the rest of the body symbolically washed and anointed. Previously, it involved an actual bath, then it evolved into washing and anointing specific body parts (i.e. they were touched in these places by the temple worker), and now it is all symbolic. The issue then moves away from changing modes, to one of authority, which demonstrates how this common LDS apologetic argument fails.
Deification/theosis has always been a teaching of Catholicism/Orthodoxy, and was never lost.
Temples are still found today. Catholic parishes, cathedrals, basilicas, etc are all “temples” (indeed, in the Eastern Catholic and Orthodox churches, these buildings are frequently referred to as “temples”, and are referred to as such in the liturgy). Our sacred buildings have much in common with the Biblical Temple(s), not only in structure, but what goes on therein. For example, church buildings are frequently divided into three general areas, there is a sacrificial priesthood, there is a flame that burns continuously, bread, psalms sung, purification with water prior to entry into the building proper, and on and on. The temple was never lost, and Catholic churches and liturgies have more in common with the ancient Temple and Tabernacle than LDS temples (baptism for the dead and sealings were not performed in the Jerusalem Temple, for example).
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Yes, Tex, you did bring up Reconstruction.