This is pretty much my own view, I think we are closer to the limits of engineering than speculative science assumes. They always use numbers that assume very compact, efficient and reliable drives. It may be that the best fusion drive will always be somewhat clunky. They also rely on the prospect that protecting the vessel at speeds a large fraction of the speed of light from collision for decades or more without a single failure is possible. Interstellar travel with realistically achievable machines is very difficult and dangerous.

Full knowledge and exploitation of either gravity or quantum entanglement could change the entire conversation. Until then, Starshot propulsion using a nano swarm approach could put inexpensive sensors into orbit around Proxima Centauri in 20 years with radio wave or pulsed laser responses containing imagery and other planetary data taking approx 5 years. This technology currently exists.

the prices at Disneyworld are outrageous!