[Lord Benendearu]

Honestly, I think CGI is an improvement to tokusatsu, but only when used to complement the practical effects, not replace them in its entirety.

When I watched the pre-CGI era liveman, I put many of the mecha battles on fast forward, as they felt really identical to each other: Just two giants wrestling for a bit and then the robot using stock footage as finisher.
Part of the appeal in newer tokusatsu is the hero(es) unlocking new abilities/weapons/mecha from time to time. CGI has the power to make these abilities look distinct from each other, making many of the fights unique.

A good example for me is Kamen Rider Ryuki. While the early CGI looks bad, it does give each rider and his contract monster a unique fighting style. Compare the rather graceful style of Ryuki to the more pragmatic and ranged style of Zolda, which are both accentuated with CGI. In this case, the CGI is used to complement the battles, as the Riders are still people in suits fighting each other.

An example where CGI just went plain wrong was the third season of Garo, Garo Yami o Terasu Mono, as all of the heroes' armored forms and monsters were CGI creations, instead of real suits. The exception is a cameo of the original Garo suit near the end. In this case, the CGI almost fully replaces the practical effects, ruining the illusion these characters are 'real'.

To conclude: I consider CGI an improvement for tokusatsu when it is used to complement the battles. If the creators don't use CGI, we'd still be stuck with wrestling matches between boxy robots and monsters, finishing the fight with the same stock footage every episode.