AX weapons are available to all, zero hrind required. Scouts can be damaged by normal weapons, zero grind required. Entering incursion susyems is 100% optional, so everything that happens there is optional by definition.
Thargoids need to be an active threat.
I am fully with you in that they are still going to be optional, and should become an actual threat instead. However, that requires every player be able to fight them without first preparing a gimmick loadout. Like with pirates - you just need a decent shield, some decent guns, some skills, and can deal with most pirates; then if you want to attack wings of Anacondas in threat level 5 USS, you need something more high end, engineered etc.
The same should apply for Thargoids. I fly this, for example. I should be able to expect at least a decent ability to deal with Thargoids without throwing away the engineered weapons, replacing all internals with hull and module reinforcement, and swapping back and forth between the normal and the Thargoid loadout all the time.
Plus, there's the thing about taste and preference. I have checked out the AX and Guardian weapons. Not even a single laser. The people in charge of Thargoid content at FD must hate lasers. Le sigh.