iPhoto vs. Photos

Here are some user tips from Photos for Mac  User Tips that will help you in your transition from iPhoto to Photos:

Notes on Migrating an iPhoto Library from iPhoto to Photos for Mac 

External Editors in Photos Are Here

Photo Editing Extensions for Photos for Mac

Post 9/30/2018 Printing Options for Photos - Apple Community

Ordering Books and Calendars on a Mac that cannot be updated past El Capitan 

Use Project Extensions to order print products in Photos after September 30, 2018 - Apple Support

Create and order print products in Photos with Project Extensions - Apple Supports

Can we assume that you're running Photos V 5.0 and Catalina 10.15.3?

Like iPhoto in what way?

I can't believe they didn't make an upgrade path for iPhoto users for the new OS.

Given that they ceased developing, shipping or selling iPhoto almost 5 years ago, and replaced it with a free and more powerful alternative, I'm not sure why you think they would.

If you don't like Photos, and many don't, there are alternatives by other vendors.