Staying in 1.7 is not only a dumb resistance for change, its a dishonest way to fool new players and (mainly) modpackers and server admins to stay with a very old version with more problems and less features.
Man, i will list just some amazing things for those guys Mojang introduced starting on 1.8:
- Banners and Shields (medieval hype YAY);
- Rabbits (i only miss them being tamable in vanilla);
- Polar Bear;
- Armor stands (i suffered a hell back in 1.6 when i tried to install a armor stand mod);
- Spectator gamemode (good for Hunger Games-styled gameplays);
- Grass paths (great way to make makeshift roads to ride your cool horse and guide yourself);
- Arrows with potions (very interesting mechanics);
- RESOURCE PACKS (change audio, textures, far more things than before);
- DATA PACKS (1.13);
- Loot Tables (with them adding items in loot from other mods became far more easy and acessible to pack makers, provided the mod use the system propely);
- Recipe JSON system (1.13?) (same of above);
- The whole structure system (i will talk about below);
- Command Blocks;
- Customized world type (its a very powerful mode to play);
- Buffet world type too (1.13);
- End civilization;
- SHULKER BOXES;
- ELYTRA!!!
- HERE'S JOHNNY (dont remember the name of the mob, is a blue villager);
- The fancy map related to the mob below;
- I already said Data Packs?
- OCEAN STUFF! FINALLY (1.13);
- The new terracottas (people hate it at first, but with proper handling amazing buildings can be made;
- THE FLATTENING (1.13) (It would turn things far more easier for pack makers, everything separately for me is better);
Dont like the cooldown system introduced by Combat Update? Here.
Everything became more clear and nice to tweak in my opinion. Even for mods it really impacted. Remember the old AtomycStryker Ruins mod? Vazkii made Pillar, which use the vanilla structure system and is far more easy to make than the former. There are also other examples similar in which a new replacement mod does things far less shady than their precursor and uses more the available vanilla systems (perharps NEI > JEI can count).
There only a small couple of mods i lost, but i would say its more because of Bukkit drama and shutdown than the 1.8 transition: TrainCarts (i still waiting for someone to make this), perharps Lockette (but Vanilla introduced a way to lock chests already), the permission system (althourgh i dont play multyplayer enough and with so much people to actually require it) and any mod to change the Villager models to Humans (i think today this would be a violation of EULA, but MCA is somewhat still going).
Anyway for any modder still coding only for 1.7: PLEASE dont force your players to stick with a version so old and with so few features Beta was good but this new versions are EXCELLENT, such amazing RPG-esque tematics for me were decisive to add a new breath to the game.