They've been around since 2008. They released a huge major version change (4.0.0) just 2 years ago.
They've released 12 builds in the past year[0]. They released 3 builds in one month last December. Two weeks ago was their most recent patch. Here's the most recent patch from two weeks ago on this "Abandonware". They have Mac/Windows/Linux specific fixes as well as fixes to their API. They're not just fixing bugs either, new improvements have been added.
Sublime deserves all the money they make. The price is super reasonable. You may be confusing "Abandonware" with "Mature software that doesn't need any major fuck-up changes anymore because all of its users love the way it works and happily spend money on it"
BUILD 4148
14 Mar 2023
Various syntax highlighting improvements
Last tab in a group can now be selected with alt+9 (Windows/Linux) and cmd+9 (Mac)
Split View retains the original view's viewport position
The window title now indicates whether Sublime Text is running with administrator privileges
Improved indentation detection for files with many single space indents
Fixed first character beyond ASCII range not being decoded/encoded for short code pages
Find in Files no longer cancels ongoing search with a renamed buffer
Fixed regression where ./ wouldn't work in the "Where" field of find-in-files
Fixed find settings confusion when run immediately after find_under_expand
Fixed minimap viewport highlighting not working when color schemes specify a text background
Reopen Closed File now uses the window's file history by default rather than global history
Fixed annotations displaying incorrectly when "ui_scale" is set to something other than 1
Fixed issue where the command palette could consume key presses while not having input focus
Fixed syntax-based folding not working correctly with some indented code
Fixed backtracking bug where tokens were being dropped
Fixed some hangs caused by syntax backtracking
Fixed tabs of deleted files incorrectly showing as modified in some cases
Fixed word wrap wrapping early in some cases
API: Added Window.num_views_in_group
API: Fixed inconsistent focus after Window.open_file
Mac: Better support for running as root
Mac: Added workaround for Monterey bug causing scrolling to misbehave
Linux: Fixed incorrect mouse behavior at window edges
Linux, Mac: Attempt to find the license key for the user when using sudo
0: https://www.sublimetext.com/dev