It feels like you're trying to call out specific projects here, but I'll bite and talk about scope from the professional standpoint vs hobbyist standpoint.
In the industry, unless you're going indie, you are beholden to whatever limits your publisher imposes upon you - usually that you need to produce the game by X timeframe in order for the project to be worth investing in. This keeps projects relatively grounded (Imagine if the entire Mass Effect trilogy, for instance, had been proposed as a single game. You'd be laughed out of the pitch meeting.), and can sometimes encourage interesting innovations to work within scope. If you get close to your deadline? You have a list of nonessential features and start picking which ones people won't really miss if you need to make your game on time.
Simply put, hobbyists don't have these limits. Most folks here at PokeCommunity will never have to worry about making deadline, simply put, because it's not their job. This leads to people deciding that they can promise big things, since they're not on deadlines. (If you guys remember the fangame pet peeves thread, I mentioned a lot of scope issues that fangames tend to have) Unless you're super hardcore into making it, writing an engine for your Pokemon fangame is probably a waste of time. Unless you're super hardcore into the design aspect of it, incorporating 721 Pokemon is a fruitless endeavor - Players are NOT going to use all 721 Pokemon, and I find it extremely doubtful that they'll want to catch 'em all in your fangame in particular when it's incompatible with all official games(NO I AM NOT SAYING TO MAKE YOUR FANGAME COMPATIBLE WITH OFFICIAL GAMES SIT DOWN), so why even try to balance your game to account for finding 24 Pokemon on Route 2? This fatal flaw, in some ways, comes from how comprehensive the toolset of Pokemon Essentials really is - it offers so much content that several developers feel committed to using it all rather than focusing on what could be a compressed nugget of core gameplay or storywriting(because let's face it - a lot of people who don't use fakemon are more interested in telling a story in the setting of Pokemon).
To answer your question, pokeconstructor, I think it's worth thinking of big projects, but I think you should gradually grow into them rather than start with an "All the regions 721 pokemon all bad guys pokemon contests snag em all everything rebalanced doctor who crossover mega evolutions for everyone" grand spectacle that will never see the light of day(incidentally, inb4 someone says "well I'm doing all that but I fully intend to finish it").
Just because you've got a large set of tools and shouldn't have to use all of them on a single project.
