I'll try to break it down for you, from my perspective so bear with me.

I don't want to take the time to do the spoiler tagging, so a fair warning to anyone reading, spoilers for hyouka below.

.

To start, I haven't seen Chuunibyou, so I apologize in the fact that I cannot relate. This being said, I've seen a fair share of Romance anime, and consider myself a fan of romance (as girly as that sounds).

Next, Hyouka, starts with a monologue talking about how Houtarou's view on life is that he wants nothing to do with anything that requires exertion, because he thinks that a "rose-colored life" is nothing special, or for him.

The entire anime revolves around how Houtarou just cannot say no to Chitanda, frequently usurping his dogma on life, getting him to do things he normally wouldn't, for the sake of satisfying her curiosity. Furthermore, this is further reinforced in how, near the end, he goes out of his way to satisfy his own curiosity on an old teacher.

There are a multitude of moments where Chitanda and Houtarou are face to face, about to kiss, but get embarrassed and back out (or similar situations which unarguably seem semi-romantic in the least).

You get the implication that both Houtarou and Chitanda have feelings for each other, but it is never outspoken.

Finally, in the last episode, Houtarou is walking, holding an umbrella in a super saturated scene. He states that he doesn't belong there, his dogma is being broken and that he can't see Chitanda.

At the final scene, I could go into the visuals, further representing a repetition of breaking into a completely rose-colored life, as they walk toward a colorful sunset, leaving the twilight encompassed land behind to further exemplify the feeling of crossroads and a brighter future, but my argument is solely with the writing, not the direction.

Afterward the parade, when Chitanda finds him, they go on a walk and they talk about the future. Everything looks beautiful as they talk about what they will do in the future. Chitanda's distraught over the fact that she thinks her home is small and neither insignificant or significant and how she is trapped. Immediately afterward she calls her land lacking potential, beauty and that she wanted Houtarou to see it.

But the way it goddamn ends, jesus christ... They give Houtarou a great line, basically saying that he'll stay with her in the area which was lacking potential and beauty. Then, the next part I liked so much, where it broke the thought and what he said didn't happen.

But, it doesn't really give anything back.

It ends so anti-climatically that I left feeling let-down. Nothing really "ended".

Of course, we've known that Houtarou's changed (from the latter half of the season). We know there is feelings between him and Chitanda. We know that Satoshi and Mayaka are likely going to be together in the future. Thing is, is that nothing is cemented. Houtarou and Chitanda don't confess anything or promise anything to one another. Houtarou isn't shown acquiring a drive for something (unless you count his dabbling into detective work really drive, where it seemed more as him resigning to some occupation). Satoshi doesn't accept Mayaka's feelings. This isn't an end. It's a beautiful second to last episode, where the next episode, Houtarou will say, "Chitanda, I was thinking. What if I took over the business side for you?" Satoshi would go on a date with Mayaka and explain his concerns, but admit that if it's her, he is fine with becoming obsessed (or something cheesy).

TL;DR The last episode takes so much time to already establish what we already know about the characters, but does nothing to resolve the plot or actually climax. The anti-climatic feeling really contradicts how great the art and animation of the last episode is.

I guess you could argue that the reason Houtarou doesn't say anything to Chitanda is that he is so focused on becoming a detective that he doesn't want to give it up to be with her; but it's pretty well stated that Chitanda takes up so much of his attention that I would find it surprising if that is the case.