In this paper, we systematically analyze various methods to reduce the computational complexity of tensor product, a key operation in $E(3)$-equivariant neural networks. In particular, we highlight that the speedups reported in previous studies may come at the expense of expressiveness, and present metrics to measure expressiveness and interactivity. We propose a simplified implementation of the Gaunt tensor product (GTP) that uses a spherical lattice directly, and experimentally show that this method yields a 30% speedup over the existing MACE inter-atomic potential learning. Finally, we present the first systematic microbenchmark results for various tensor product operations, highlighting the gap between theoretical time complexities and practical performance.