It’s horses for courses. 3 bolt road pedals and shoes are tangibly better on the road. The platform is wider and longer, meaning you rock around less. The shoes are stiffer for a more fixed position. The stack height is lower for greater efficiency. The pedals are weighted so that they ‘offer’ themselves up as you clip in. If yours don’t, it might be that you need new bearings or different pedals. I use SPD SL pedals which are better in that respect than the Look Keos that I previously used. Since the cleats are generally plastic, you get less of the annoying metal-on-metal squeaking that can plague Shimano SPDs in particular.
In reality on your average road ride, you tend to clip in and out fairly infrequently (and you can generally time yourself approaching traffic lights to clip out even less) and you don’t tend to need to walk much, so the time spent pedalling (where the benefits are significant) vastly outweigh the drawbacks of walking stability and ease of clipping in for a very brief time
Are SPDs ‘OK’ on the road? Yes, with a few caveats. I use them on my gravel bike and tend to do quite a few tarmac miles on most rides. The caveats are:
1) You do rock a little more on the pedals.
2) With the wrong shoes (ie not stiff enough) you can get hotspots from the smaller contact area.
3) You need very stiff shoes. I use Sidi Tigers which basically use the same carbon road sole as their road shoes with some (not much) grip.
4) They are heavier, but when you combine the total bike and rider weight it adds up to less than 0.1% overall.