I can only tell you about my personal experience, but I bought ED on it's release day and played keyboard and mouse for 4 years. Then less than a year ago I finally decided to get a Hotas, especially because flight sims were finally making a comeback (I played lots of flight sims in the 90's, 00's), so I could use it not just for ED but for several other games like X-Plane11, Il-2 Sturmovik, Rise of Flight, DCS, Take Off Helicopters, etc.
While playing ED with KB/M never gave me any disadvantage at all, control was very precise, practical and pleasant, playing with a HOTAS is just so incredibly satisfying... I know it's mostly immersion, and it's hard to explain properly, but it just feels fantastic. If you plan on playing other sims as well, the I truly recommend you try one. It cranked up my playing time by several orders of magnitude, and even trivial things like flying over some hills on a planet, approaching a planetary port and docking, or doing an invert dive into some canyon just feel fantastic, even just faffing around with the ship becomes actual gameplay. Even when flying "softly" like roleplayinmg a passenger ships it's still incredibly enjoyable,
I started with the Thrustmaster T160000M HOTAS, which while not the cheapest it's still not that expensive either, and throttle/stick can even be bought separatly making it cheap to replace if needed. (it also has pedals but I never bought them due to extra clutter, and the stick has twist so no need for pedals for yaw). It's a very nice entry HOTAS, has a nice feel and loads of buttons, hats and axis. Not great on build quality though, but that is somewhat offset for being cheap to replace individual components. I loved my initial experience so much I have then felt confident to get a more costly HOTAS and upgraded to my current Logitech X56.
The only downside (besides needing to spend money of course), it that the first moments might feel a bit frustrating, until you finally get the bindings to your liking. This can actually take days or even weeks until you feel they're "just right". If you ever had to adjust the mirrors on a motorcycle, it's the same feeling
Also, at first you'll feel like a noob again, until you get the same levels of muscle memory you already had with the mouse (anmd until you can finally remember what buttons are bound to what

). At least I did, but once you overcome it it's just truly fantastic.