Odoo suffers from others issues though.
Not sure if this is still the case, but the mix of inline Python 2 Flask + XML was basically tech debt-as-a-service.
Also the very ugly death they gave OpenERP/Odoo on-premise.
It's Python 3, no Flask (but werkzeug) and XML templates.
It works for hundred thkusand clients, and you can install Odoo on premise as you like. I'm 90% dedicated to that.
So... explain the "tech debt" thing, as I don't get it. You don't need Rust or microservices for every use case. Don't be fooled by marketing style "old style technology" bias and set up an account. PostgreSQL with synchronous workers works perfectly for most people.
I am absolutely not a fan of "new style technology" as you might have understood.
I used to run Odoo on-premise for a small company about 3-4 years ago. The upgrade path (with the OpenUpgrade fork) was awful, many features (that WYSIWYG editor, Odoo Studio?) were locked to the cloud version, and there was little to no documentation.
IIRC we even had to drop it because the delay between on-prem updates & cloud updates was too high.
And there were mentions of Flask in the logs, so no it wasn't just Werkzeug (which is synonymous with Flask since its inception, anyways).
I do not have fond memories of editing invoice templates blindly.
Ofc the cloud offering has much more, but you have to consider that no other major ERP software comes with the engine 100% opensource, in the kind of market. So yes, you may feel Odoo community a bit incomplete and probably don't want to pay the cloud version. But the alternatives are SAP, Microsoft, Oracle, some very fragmented open ecosystem, or some 90's GUI custom ERPs, right?
I can tell you we use Werkzeug and not Flask, have reverse proxy nginx, use postgresql, and I don't see a lot of tech debt in that.
Not much AI, all the reviews are manual and kinda strict.
Also the very ugly death they gave OpenERP/Odoo on-premise.