"But I Wouldn't Play it As-Is"

Whenever I see a Basic Roleplaying review, I hear the caveat, "But I would not play it as-is," or, "This is a book more for game designers."

My question is, why not?

BRP is "there" for 95% of what you need and is far more complete than many games. Flipping through the book, I see it has enough to work like a GURPS, a framework for creating games without worrying about converting too much.

I play GURPS "as-is" and Cepheus Engine, too. I play most versions of B/X as-is.

BRP ships with many optional rules, along with all sorts of subsystem choices. You will need an equipment list for a specific setting, and you are good to go. The gear lists here are a good start. You could review the skill list and tweak them to your setting, but the skills work fine for almost any setting. Much of what you need is already in here, like a fate point system.

I don't see why this isn't "ready to go" for most genres.

Some things don't need to be converted. Starfinder has many leveled weapons and defenses, and those will never convert in the right way. The stock sci-fi weapons here are good enough to reskin as whatever you need, and besides, a laser pistol is a laser pistol.

Gamma World is another one of those games. This is a CON-d6 system. While the missile and energy weapons work fine, forcing players to use a d4 dagger or a d8 sword versus 35+ hit-point starting characters makes players laugh at old-tech weapons like they were butterknives. Gamma World has always had this problem. The monsters are also CON-d6, so converting them is touch compared to anything B/X. Again, forget the weapon damages and monster hit points and go by size and stats. Again, a laser pistol is a laser pistol.

Mutations, if you use the Gamma World list, must be converted. For example, if one does as much damage as a laser pistol, use BRP's laser pistol for the damage.

These conversion problems exist for any game that strays too far from B/X. Even 5E has this problem, so sticking to B/X-style numeric ranges is always the best bet for gaming. Scaling systems are horrible beyond the flat monster HD ratings in B/X. A level 8 character in B/X still does weapon plus modifier damage, like a d6+2, but they have a better chance to hit (thus, more significant overall damage). That 8 HD (30 hp) monster rating is still valid at all levels. You get a 5E, and level 8 characters are doing 25-40 hit points damage a round (where they were doing a d6+2 at first level), and 8 HD does not mean 8 HD anymore; it is more like 1 HD to that level 8 character.

The damage scaling Wizards introduced broke the game. It has been this way since 3E.

Hit points in BRP are calculated from ability scores (CON + SIZ / 2). Since this is all based on real-world numbers, you are not concerned with arbitrary hit-die systems. A dragon has a lot of hit points because it is large and has a high CON.

Thus, weapon and character damages are on the same scale, from low level to high. So, even conversions are easy once you adopt BRP's real-world measurements and stick to ability scores before made-up numbers. "How things work and feel" will change since you are in a more grounded system based on actual numbers, without much guesswork.

BRP is ready to go out of the box for most genres and games.

I recommend creating your unique "subsystem" to tie the rules to the game world. Runequest has the runes system, which isn't in this book. Call of Cthulhu has expanded insanity rules. You can make your own! Let's say you were doing a "Star Force" game with a "light side and dark side" sort of system, then make a fun, two-sided alignment system that works well with a percentage system, and this will be your "setting-specific rules" that you will snap on to the game.

You don't need to be a game designer to play this, nor do you have to write a game based on this.

But the game gives you plenty of room to craft and design if you want to dive in.