i agree with this because of a few things
Q2's very smooth textures compared to how incredible the Q1 textures look in high fidelity on a modern system. the sharpness of the textures in Q1 under the right settings naturally looks more appealing than the muddied Q2 textures.
Q2 has comparatively very slow projectiles (obviously excepting hitscan like machineguns and railgun) to Q1 (from memory), i'm very sure Q1 was much faster in movement and gunplay.
Q1 also has very satisfying fantasy environments which are overall more pleasing to play than the brown-red warscape of Q2. not to say that stroggos is a bad setting, because it's really quite incredible moving through these alien military installations, but it achieves what it sets out to do in making you feel like you're traversing a desolate alien landscape where, much like with the strogg, it would be utterly devoid of life without humans, which makes you feel very uncomfortable to be there. Q1's technomagic/gothic/lovecraft scenarios are incredible to explore because they inspire rather than demotivate.
Q1 also had far better enemy design than Q2 even if most enemies are zombies in one form or another, but enemies like the gladiator in Q2 are pretty inexcusably bad. Q4 stepped up enemy design from Q2 by a huge leap, and i can really, really appreciate that.
dare i say Q2 has worse sound design than Q1? hard to say, i played a lot of both on mute through childhood, school, uni, holidays, plane trips. Q1 has really satisfying sound design, like some of the original doom sounds, but Q2 does also.