Thanks for your clarification. I understand now what you have done. For each festival, you have added one instance of tithi, with each instance including masa and paksha too.
The idea of the template was to standardize the dates across all Hindu festival pages (show masa, paksha, tithi; handle both amanta and purnimanta tradition; use IAST to indicate the correct pronunciation of the masa, paksha and tithi). You are right in saying that the template is complex; it assembles any festival date from instances of masa (12 instances - chanitra, vaishaka etc), paksha (2 instances - shukla and krishna) and tithi (15 instances - prathama, dwitiya, etc.). And all these instances of masa, paksha and tithi have "IAST transliteration" defined.
Since your changes broke all the pages that used the template, someone else has corrected the dates in many pages in a rather unusual manner (some pages are still broken):
For example, Krishna Janmashtami is now showing "Shraavana 23 (amanta tradition) Bhadrapada 8 (purnimanta tradition").
Would be nice if you can correct the pages of the various festivals to use the data that you have added. And also, provide IAST Transliteration in the wikidata entries so that pronunciation will become clear.
Finally, there is a page "List of Hindu Festivals". There is a summary table that shows the dates of all the festivals, at a glance. That table too is broken now (since the template is broken). Would be nice if you can fix that too (easy way would be to remove that table but that would subtract information from wikipedia).