Bladesg

WLs isn't easy compared to other systems. Certainly there's plenty of fish in there but what works elsewhere doesn't always work in there. 
I'm no expert fishing WLs but you need to think more about where you're fishing, at what time of the day. There's more to it than that but it takes perseverance. If I had a dollar for every time I scored a donut in WLs... 🙄
Imo the fish in WLs have it pretty easy because they get fed by residents and the system is on most days being replenished by sea twice a day. I've had days there where I've presented virtually every lure I own at them and 90% of the time they won't even take a sideways look. If they do, they might follow briefly then turn their noses at it. 
There's many plastics that work on bream in WLs, I'm not going to make any suggestions because I'm guessing that if you chase bream on plastics you most likely already own the ones that work and it's no secret.
Good luck with it. I might fish it myself Saturday A.M

Have you tried getting the bait down deeper? When they're finicky sometimes I'll get the hooks down 1-2m

I tend to think that using clips on a jighead has more effect on the action of the lure than when fishing hb lures with clip.
99% of the time I use a loop knot to both jighead or hb lure.
Removing the split ring from the bib of a lure can also improve the action in my experience.

Easy to get disappointed sometimes no question. Truth is, if fish are not in the area your bait is you won't catch fish. Doesn't matter what prep or research or even how good you are or think you are, you won't catch fish.
I fish with a mate on a boat occasionally and this season the garfish have been difficult to find in numbers and size, we've tried plenty as garfish are my fav table fish.
Like all types of fishing it takes practice and learning. Take notes, photos or whatever of what works, when and you'll work out the how. You might notice that on certain tide phases, moon phases, time of the day ect ect that the fish come on the bite for instance.
What's the depth of your trace below the float? Photo?

The Gar are being caught on most jetties, but in saying that, this year has seen less caught from the jetties - why? only the fishing gods know.
The last few years, Gar has produced well but it has been very up and down this year, although the boaties have done better - but there have been many reports where they have struggled too.
But like jackman says, the Gar just were on.  You might think, 'but all the time' ... sometimes yes.
Were there any others going for Gar and catching them?  If there were and not catching then it wasn't just you.  If they were catching, then watch what they are doing, go and stand near them and look at their set up. Have a chat to them.
Many of the regular Gar fisho's on the Port Noarlunga jetty have all said this year has been slower.  There have been many times when talking to the other regulars they mention nothing being caught for the whole week, then the following day you hear that the Gar 'were on'.  If we knew when the fish where to bite guaranteed we'd all be down fishing, but that would then be boring.
Ok......
- Gents (best) - Gar flesh a 2nd good option
- Burley (could rub some stale bread between hands so crumbs fall into water, have a burley bucket with pellets into dangling in water or a very small spring on leader to put some burley) - but don't over feed them, just enough to entice them, then back off on the burley.
- Light set up (6lb line is good)
- Float (as light as possible)
- Hook (size 10, 12 long shank) or what I tried on the session was size 14 short shank (worked well)
- Rod (I like 6'6" to 7'6" length with a nibble action tip)
- Reel (something small/light, say around 1000-2500)

Easy to get disappointed sometimes no question. Truth is, if fish are not in the area your bait is you won't catch fish. Doesn't matter what prep or research or even how good you are or think you are, you won't catch fish.
I fish with a mate on a boat occasionally and this season the garfish have been difficult to find in numbers and size, we've tried plenty as garfish are my fav table fish.
Like all types of fishing it takes practice and learning. Take notes, photos or whatever of what works, when and you'll work out the how. You might notice that on certain tide phases, moon phases, time of the day ect ect that the fish come on the bite for instance.
What's the depth of your trace below the float? Photo?

I've never used glue, or hooked over the eyelet or anything like that; maybe I'm just used to realigning my plastic that it's a force of habit.

If you are going for garfish , I suggest always move your bait a little ,sometimes they don't even move your float ,they are just sucking on the gents ,just light lifts now and again as sometimes you will feel some weight ,and you know they are there . Also check your maggots on the hook , if they have had the guts sucked out , you know they are there ,so you just have to work for them . As said above I have fished for over 40 yrs ,and Gar can be very finicky at times ,and they will do your head in . The last trip I only managed 7 gar ,the time before 37 gar ,the time before that NOT ONE GAR . So don't give up , Gar is one of the harder fish to master at times , but worth the effort as YUMMO to eat .
CHEERS 

Never used glue on any plastics, have never felt I've needed to.
Most often I'll do exploratory fishing in an area to find what's working on that particular day in that area. I'll have usually a half dozen plastics in my pocket (not in my tackle bag) and I'll change colour and or type of plastic in one particular area to determine what they're liking. Sometimes I don't have to change things up because they hit the first one I cast but they definitely hit different colours and types on different days.
If I glued them and had to re-tie a new jighead everytime I changed I probably wouldn't bother.

Most of the SP fishing I do is for bream in various systems, occasionally chase mullies and snapper on them too but I've never really been bothered by fish pulling the plastic from the jighead. Sometimes we get loads of leatheries on a snapper drop but I'll switch to a metal jig or sinking stick bait or we move altogether 😂
As an example most guys I've come across that fish plastics for bream predominantly use a 2.5" motor oil grub, for good reason but having said that for me I've easily caught more fish on different shapes and colours and wouldn't rank the motor oil grub in my top 5 picks. 
I really enjoy that part of fishing too where I can find out what's working where and when.

Yeah getting pantsed is predominantly a micro pinkies on plastics problem. Heaps of aggressive hits that dont hook up when you strike is the issue.

But I specifically bought the ZMANS to target pinkies that hang around bait schools so white is a half decent match - it could be better but it will do

Just what truly is the worlds best fishing rod?
At least I can truly say, it ain't that rod....

Trust me they work!

You guys obviously don't look real hard. These are available and have been for at least 4 weeks at a very well known local tackle shop