You don't have to go to crash sites. Probably lore-wise the aliens' life support runs out and they die after some time, then X-Com agents clean up the mess after it's safe. But once the ship is down, you can safely ignore it without it impacting your score. I find that simply shooting down tons of aliens gives you a huge score boost and can easily make up for the occasional battleship you ignore. In the long term, just make sure you aren't ignoring any countries. If you let too many of them go, you can lose them game despite doing well.
Mods are of course another answer to spice up the game. Luke's UFOs is an excellent way to make crash sites a bit more interesting, especially with the larger craft because the interior design will be different almost every time. I believe Hobbes posted a mod that gives more terrain variations across all types of sites. And my Air Weapons mod makes fusion ball weapons a lot stronger so if you're willing to spend the elerium, you can destroy the smaller craft outright and even take out battleships without taking too much damage. Note: my Air Weapons mod actually makes air combat more difficult in general, but makes it scale better overall.
If too many soldiers die then I can hire rookies and start all over again.
There is much to be said about advanced technology boosting the effectiveness of your troops. It really helps you get back on your feet when you lose trained personnel. If you feel the tech advantages in your game could use a bit of a boost, there are mods that give even more options. I'm not well versed in these options, but I have a mod that tweaks the power and flying suits to grant strength or firing accuracy, respectively. It's very nice for rookies.
Luke's UFOs - this mod meets with my approval!
https://www.openxcom.com/mod/lukes-extra-ufosTerrain Pack by Hobbes - I haven't used this mod but I believe it is used in FMP.
https://www.openxcom.com/mod/terrain-packReaver's Air Weapons - my own mod
https://openxcom.org/forum/index.php?topic=4791.0In posting this I have come to the realization that I don't have a page for this in the mod portal yet. That will be fixed eventually!
Reaver's Soldier Classes - also my own mod
https://www.openxcom.com/mod/reaver-039-s-soldier-classesThis one changes armor in a way you might find useful, though it also makes some other major changes you may or may not like. Still, having hiring options may further assist you in getting back on your feet after losing soldiers.