It appears there's an issue where loading the page to view an activity in Garmin Connect web is slow if the run/walk graph is on. This issue is present on all runs but seems to get exponentially worse as the time of the activity increases.
Noticed some issues when viewing activities, especially long activities, where loading the page was EXTREMELY slow. This was the same across different browsers/computers/OSes (Chrome and Firefox on Windows 10 and Chrome on Android). Loading a recent long run of four hours takes 12-14 seconds. Loading up a recent 100K race takes a couple minutes, and for a recent 100M race the page hangs for literally 20 minutes before the activity loads. Panning the map is also quite laggy even once it loads.
Noticed I wasn't having this issue when looking at an older race recorded on my Fenix 5 which doesn't not have run/walk detection. Tried some troubleshooting and as soon as I turn off the run/walk graph, those same 100K/100M races above all load in 2-3 seconds (tried both Windows and on Android). The lag with panning the map is also gone with that run/walk graph off.
This issue is specific the graph. If I turn the map layer to run/walk, it doesn't cause any issues. The activities were all recorded with a Fenix 7.
The issue is not present on the Garmin Connect app for Android.
ETA: Also noticed enabling the Run/Walk graph GREATLY increases the memory usage. Without it enabled, a Chrome tab for the 100M run uses 377 MB of memory. With it enable, it uses a comically large amount of memory, 2 GB.