Throw as much ram at it as you can. I see people saying they’ve got their startup times down to “only 210 seconds.” And they’re using an SSD.
No SSD here - instead 8 x 4TB Western Digital Red (5400 rpm but 256 mb disk cache) and 128 gb RAM - and with my folder showing a quarter-terrabyte of data, and a 1 tb rolling cache, my startup time (time from clicking the icon) is 133 seconds, on an i5-12400. No overclocking, but the RAM is Kingston Fury at 3600 mhz by default.
You can NEVER beat more RAM, especially with any Windows application as heavy as MSFS. 64 gb seems to be a realistic minimum if you don’t want to be swapping all the time.