Output in xml is a little more difficult than cvs but not a lot.
The complexity is the bidirectional communication protocol, with the associated authentication, validation and error reporting at transport and application levels. Do this several times in each jurisdiction then multiply by the number of countries Manger supports and the task becomes well beyond NG Softwares resources.
For example in Australia just for payroll DSPANZ - About STP Products
In Italy https://www.fatturapa.gov.it/export/fatturazione/en/normativa/f-2.htm?l=en
In the UK Making Tax Digital for VAT as an agent: step by step - GOV.UK
With tool development at a relatively early stage http://holodeck-b2b.org/
That is why an intermediate data communication supplier is more achievable.