If you want to keep that Mac as a platform for running old 32-bit applications (like games) that won't run on modern Macs, I could see putting a little bit of time and money into speeding it up. (You can get a 16 GB (8 GB x 2) RAM kit from Other World Computing that would bring your total memory up from 4 GB to 20 GB. OWC also sells SSDs that are designed to get the best performance out of that Mac's slow SATA-II bay, and FireWire + USB enclosures which would give you the best performance (though not barn blazing performance) for external drives).
If you are not tied to 32-bit software, and want to run current applications, it's time to retire that old Mac and move on. Very little current software is available for High Sierra, even compared to a couple of years ago.
Vendors like Microsoft & Adobe have a policy of supporting only the "most recent three" – which are now (Sonoma, Sequoia, Tahoe). Even when it comes to applications whose vendors support older versions of macOS, you need
- Catalina or better to run the current versions of Firefox, LibreOffice, and the commercial Affinity V2 suite
- Monterey or better to run the current versions of some other third-party Web browsers
MacTracker does not have CPU benchmarks for your iMac, but it has these:
- IMac (21.5-inch, Mid 2011) (2.8 GHz) – 678 / 2018
- iMac (24-inch, 2024) (8/8 core M4) – 3721 / 13716
- Mac mini (2024) (10/10 core M4) – 3748 / 14467
That's a speedup of more than 5x in terms of raw CPU power. The M4 iMac and M4 Mac mini also come with 16 GB of RAM or more, and have SSDs that are much faster than the mechanical hard drive in your 2010 iMac.
If you upgrade to a M4-family Mac that has at least 16 GB of RAM and at least 512 GB of internal SSD space, I think you will be very pleasantly surprised at what a difference 14 years of technological improvements have made.