Are you sure that they're significantly minus on shield even with cancels? I also didn't say he has true blockstrings, what I meant was that most pokes chain directly into strong mixups or DT away, among other things (forcing your opponent to bail w/ buffered rolls all the time is a strength, not a weakness). As Lucario's opponent you can never really expect to get an OoS punish, and that means you have to be evasive (he can probably match or exceed this with a good DD) or wall him out.
He does have reliable pokes with proper spacing, too. Even little things like SH instant fair (3 frame JS + 4 frame fair is a frame 7 hitbox, right?) can help by cancelling off of a shield into DT away, or DT in should you get a direct hit or read an attempted roll/shield grab. Ground pokes are a similar story, although I guess you need to be more careful spacing out grab ranges.
In general, here's how I see his neutral game:
Good dash speed and at least a few noncommittal pokes form the essentials, and let Lucario avoid throwing out attacks if he doesn't really want to, which is important given that he is most vulnerable on whiff.
A lot of his fast pokes have decent range but poor disjoint (dtilt, ftilt, fair, bair) and are most useful as counterpokes, which also plays heavily into the style of evasive DDing. If your opponent responds to this and wants to bait out a whiff by hanging back, then you have AS to deal with that. Not having overwhelming pressure/conversions out of neutral is a problem for him, but I definitely don't see Lucario's combination of tools as being lacking or otherwise exploitable, and charges and b reverse techs can only add to all of this.