I'm not sure if this is sound reasoning, because "better product" is very context-dependent.
My currently employer has migrated away from RT to OTRS as ticket system, and now moving to servicenow.
The RT instance was heavily patched/customized.
The OTRS instance was heavily patched/customized.
We try not to customize servicenow quite as much, but the less we customize it, the more we have to change the workflows in our company. And humans are slow to adapt.
With this experience in mind, the question is more: do we want to spend lots of money on a vendor-supplied ticket system, and then spend lots more LLM tokens to customize it, or do we LLM-build it from the ground-up?
If we started a new ticket system migration project today, maybe the best answer would be to start with an easily-customizable Open Source ticket system, and then throw LLM-power at customizing it.
But in this case you don't spend tokens only on your workflows: you have to patch it constantly, perform vulnerability scans, check and adapt for law changes(eg. if you in europe: GDPR or DORA), create and maintain (again security) integrations with other systems and so on.
And, most importantly, you as a corporate need an internal team to do the work and that means it's a liability to you as a corporate ... and we all know it's better to have some else to blame.
Just imagine the CTO or CISO explaining to the CEO that the data breach they had last week and that cost them millions was due to some customization they did on top of an open source ticketing system.