It helped that B5 premiered 6 1/2 years later than TNG, and CGI tech improved a lot during that time. TNG was already locked into physical models in 1987, and they had to wait for CGI tech to improve enough to (mostly) match the look of the physical models.Those were definitely the limited budgets when Physical Models ruled & CGI was expensive & new.
The Trek Production teams were slower than B5 on adopting early CGI.

