Agreed. The only reason not to try and compete for at least a WC this season is if they're cheap. The core is ready now to be supplemented with veteran talent.
The argument I see for waiting another year typically is based on wanting to know for sure if Wood/Crews/Abrams are for real and what other holes the team needs to fill plus this free agent class not being ideal fits for the team. I don't agree with that argument.
There's a bit of a difference between tanking in 2025 and making small moves to supplement the cost-controlled core. I would not call the Lowe deal tanking, and I think Williams and Soroka are good value. It's just there's no long term pieces of high end talent being plugged in. If some of these players like Bregman / Santander / Alonso have misread their market and start looking for pillow contracts, I could see Rizzo making a move. In the meantime, a signing of a Bell and a Williams that takes advantage of their liking to play in DC to get them at below their projected contracts is a good way to round out the roster.
The Nats should get around middle of the pack performance out of DH next year. Not to get too caught up in projections, but Bell 2025 projects about 5% below 2024 league average (.745 OP vs .760, and 109 wRC+ vs 114).* Add in Chappy handling most of the ABs vs. lefties (Bell's weak side), and I can easily see league average performance at DH. Contrast the to the mess last year (.690 OPS, 95 wRC+), and that's a big upgrade. About the only thing it probably precludes is an effort to sign Alonso.
in the near term, the team sinks or swims with Abrams, Wood, Crews, and Garcia. Lowe augments that well.
* those are Steamer projections off fangraphs. FWIW, the ZiPS projection for Bell is in the same ballpark - .748 OPS / 107 wRC+ (.256 / .334 / .414, 17 HRs).
https://blogs.fangraphs.com/2025-zips-projections-arizona-diamondbacks/