I was wondering what others felt about conditions and the like?
Conditions, overall, are a good thing. But they're not an unalloyed good. Especially...
So, thoughts? Game effects which effectively prevent the player from playing?
To a certain extent they're unavoidable, if only because "dead" is a de facto condition that does this. However, they do indeed suck and should be used
very carefully. Ideally, such conditions should be rare, should be hard to apply, and should be either short-duration or save-ends (with saves that are reasonably frequent and not unreasonably difficult).
Indeed, it would be good if the conditions that took you out of the game were placed on an escalating track, as with the exhaustion levels in 5e - so that each incremental level reduces what you can do, but it's only the end effect that takes you out of play (and with very few, or even no, powers being able to skip levels and just take you out in a one-shot).
Or should players prepare better so that conditions never affect them?
To an extent, it's not unreasonable to expect PCs to prepare for their adventures. And if the characters could reasonably expect to meet Carrion Crawlers, if they then choose not to prepare some anti-paralysis magics then that's on them.
But it's not really practical to expect them to prepare enough to be effectively immune to everything, nor indeed would that be a desirable outcome. For the most part, I'd prefer to see "save or suck" dealt with through system design, so that the threat can still exist but so that it's appropriately rare.