After a fun beginning that resembles a public information film from a bygone era it settles into a formula that's best described as a slightly more sophisticated offspring of 1950s post-atomic films. Action is split between monster-time and scientist-time. The scientist, however, is at least flawed in some way, figuring himself out as he goes along.
It strays from the original John Wyndham novel (1951) often but with a certain level of charm that keeps my disgust at bay each time I watch it. There are even some genuinely effective Triffid POV shots to unsettle the weak.