As the product evolves, best practice and preferred connectivity methods have been via IDT, and BICS for OLAP functionality. BW universes of old on the BAPI layer are still supported and the old UDT is still delivered.
DeskI went through a similar evolution, where it was gone, then back because of a sudden shelving and too many stayed with DeskI vs converting to WebI. DeskI went away twice and came back twice, before it was finally gone, but not really. (the security and functions still remain in the platform)
Before that with Crystal Decisions - the Excel export .dll hack was provided to get it behave like Office 95, well into 2005 on BOE XI 12.1. Effectively dumbing the system down because clients were not adhering to the published best practices from CE9.0 that stated to design the report with fields snapped to each other, otherwise blank spaces lead to additional blank columns.
We have been on 4.x for some time now, published best practice, and preferred connectivity via IDT for universes, and BICS for BW or HANA (OLAP)
When is SAP going to publish a projected end of life date for UDT and BAPI universe support to gear customers up for converting their reports, before a release comes out that doesn't have it and catches them with their pants down and unable to update/upgrade/patch to the latest release??