Taurus Aldebaran is a tank-DPS Saint with mechanics that were interesting for older metas. His kit combines delayed burst and durability: Ultimate Huge Collision marks a target and releases a heavy hit after charging, Immovable can add pressure while applying Wild Bull Mark, and his Awakened passive gives control immunity plus damage reduction during charge. He can also gain shields and even recover HP if his charge is interrupted, which gives him some survivability value on paper.
The problem is that current matches are too fast for this style. Aldebaran needs setup time to deliver his main damage window, and modern teams can usually out-tempo or bypass him before that payoff matters. Even with good base bulk, his pressure is too conditional and his overall impact is too low compared to newer frontliners and DPS options. At this point, he has no place in meta in PvP or PvE.