Balloon professional here (yes really that’s a thing) - most responsible retailers will not sell balloons for release, if we suspect at all balloons for release we refuse the sale. I have unfortunately had disputes with many grieving families and it’s a very hard line to tow when you can see they are already suffering.
Regarding balloon arches, it’s true that latex can take a while to break down, it all depends on the environment of breaking down iyswim (heat+pressure accelerates the process) - there are also more responsible manufacturers than others that use less chemicals in their production process etc. Again responsible businesses will try and go with the ones that are better.
Rwgarding helium, it may interest you to know that the leading commercial supplier (BOC) uses recycled helium, that is no longer a high enough standard for essential uses such as in medicine. So it’s already been used and now is no longer pure enough and is supplied as ‘balloon gas’, not helium as it is not just helium. It’s not perfect, however you should know that no one is mining helium specifically for balloon use - it’s actually often getting a second life through the industry.
You can now also recycle foil balloons through TerraCycle at drop off points in the card factory.
Im not saying the industry is perfect (it’s really not), but what industry is? But I can say it’s an industry that is trying very very hard and I think gets especially demonised by environmentalists. Even for electric cars you have to mine cobalt and thats a finite resource like helium is - there is no perfectly green way to live sadly but we can all try to do better and all of the big players In the industry are trying very hard!